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I ask you to consider with me a topic which is of fundamental interest to physi- ologists, whether they concern themselves primarily with animals or with plants. I take it the basal identity of the living mat- ter in all organisms and of its metabolism needs neither demonstration nor emphasis at my hands. Nor do I need to lay stress upon the importance of respiration as one of these metabolic phenomena, since it has been recognized from the earliest period as indispensable to life. The phlogiston the- ory of the composition of the atmosphere had searcely disappeared below the scien- tific horizon, before the fact was discovered that there occurs, in animals and in plants alike, an intake of oxygen and an output of carbon dioxide which is intimately re- lated to their existence. This became ob- vious to man, of course, in his own experi- ence, a very superficial study of the com- position of the air inspired and expired from the lungs showing that it had lost oxygen and gained CO,. This much of respiration was early recognized to occur also with the larger animals, and a few years later like observations were made upon plants by Priestley, and more acecu- rately by Lavoisier and Ingenhouss. Even this knowledge of respiration was not pos- sible before Priestley’s discovery of oxygen in 1774, and the very remarkable revolu- tion in chemistry that followed in the clos- ing years of the eighteenth century. Yet

* Address of the retiring president before the Botanical Society of America, Philadelphia, De- cember 28, 1904. Published simultaneously in the Botanical Gazette.

this disappearance cf oxygen and forma- tion of carbon dioxide are only the external indication of respiration, as has been long



Upon undertaking a special consideration of this topie, | found it needful to examine the recent literature ef respiration in ani- mals, the aspect of the general subject with which I felt myself least familiar. I found, to my very great surprise, that ani- mal selves very little with the essential prob-

physiologists have concerned them- lems of respiration. They seem to have been diverted to the study of the mechan- ism of gas movements in the higher ani- mals. The lungs, with their intricate strue- ture of lobes, lobules, atria and air ‘cells’; the box in which the lungs are located, with its complex muscular mechanism, and the very complicated mechanism of innerva- for the voluntary and involuntary it executes; the blood,

tion movements which and the physico-chemical relation of the gases that enter and leave it in the lungs, of those that come into it from the tissues and of these it gives up to the tissues— these are the tepics that one finds exploited at length when he turns to the text-books. I diligently examined the most modern and most thorough text-books on animal physi- ology ; such books as Foster’s Physiology,’ Stewart’s ‘Manual of Physiology,’ the ‘American Text-book of Physiclegy’ and Schaefer's * Text-book of Physiology,’ but in them I found no treatment whatever, indeed no mention whatever, of the real problems of respiration, that is, ef what is happening in the tissues, the processes of which these external phenomena are the

sign. Yet this much-studied respiratory mechanism, which is so striking in the

higher animals, is entirely wanting in the lower animals and in plants. Not finding even a elne to the literature


[N.S. Von. XXI. No. 529,

in the text-books, it was only after much search that I was able to discover. that any- thing at all had been done; and it is so little that it is almost a negligible quantity. There is an obvious reason for this, besides mere interest in the more striking phenom- ena. Iam intending, however, neither ar- raignment nor excuse, but a bare statement of what were to me rather surprising facts.


The knowledge of respiration in plants began about the same time—the close of the eighteenth century—and advanced rapidly on account of the notable revolution in chemistry which took place about this time. Ingenhouss, the Dutch naturalist, really as- certained and published in 1779 the chief external facts of respiration; at least he was able to state them essentially as they were known for twenty-five vears after his time. In 1804 DeSaussure showed that growth is dependent on respiration; that respiration is more active in growing parts than elsewhere; that it is the cause of the loss of weight to which plants are con- stantly subject; and later, that the heat set free in flowers is related to the absorption of oxygen. Not until 1833 was respira- tion treated comprehensively, when Du- trochet expounded the subject, comparing the respiration of animal and plant and showing it to be fundamentally alike in both.

Now at this point there began two re- markable misconceptions. One was thie confusion that arose between respiration and the manufacture of carbohydrates. which Dutrochet called ‘diurnal respira- tion.’ Of that I shall not speak, save to say that the great weight of Liebig’s au- thority made this errer persist for half a century.


The other misconception was engendered by the comparison of respiration to com-

FepruaRy 17, 1905.)

hustion. It had been observed by Lavoisier that the heat of the animal body was de- pendent upon respiration; the heat of the plant body was shown by DeSaussure to be related to a disappearance of oxygen; com- hustion consumes oxygen and_ produces heat; therefore, respiration is a sort of combustion. So the argument ran.

It is quite impossible to overestimate the influence that this conception has had on the study of respiration. The mischief it has wrought depends chiefly, perhaps wholly, upon a misconception of the actual mechanism of combustion, a process that has ever been the béte noire of chemistry, as the history of the ‘phlogiston’ theory well shows. To our changed conceptions of combustion I shall return later.

The idea of combustioh, however, which dominated the argument I have cited, was that oxygen combined with-carbon to form CO, and with hydrogen to form H,O. It was most natural, therefore, to conceive that the food taken up by the organism stood to it in the same relation as does the fuel to the engine, and that what happens is an actual oxidation of the food imme- diately and directly; in faet, a process pre- cisely parallel to the burning of the same food outside the body.

One evident outcome of that idea is the current classification of foods into plastic and dynamogenous, those which are useful in building up the body and those that are useful in producing heat within the body; into ‘fattening foods’ and ‘heat-producing’ foods. You are doubtless familiar with these phrases.

But if foods are ‘burned’ in the body it must be important to know how much oxy- gen enters it, and how much carbon dioxide and water leave it, so as to discern the ratio which exists between them. Plainly a basis for this must be a comparison of the differences between the combustion of foods outside the body and their ‘ecombus-



tion’ within the body. Yet, strangely, this has not been made until recently. Without giving the full tables let me show the re- sults arrived at by two observers, regard- ing two of the most common plant foods, glucose and tartaric acid. These observers assume, you will notice, that the processes are comparable. The results are stated as ratios of CO,/0O.,.

ae By respiration. 00 bustion. 'Diakonow. Purjewicz.

Tart. acid £88 106

Diakonow’s whole series shows that in combustion the carbon dioxid was always less than in respiration; Purjewicz found, with the exception of tartaric acid, and even there the difference between his re- sults and Diakonow’s is in the same direc- tion, that it was always greater, his results being absolutely different in significance from Diakonow’s. And this is a good type of the results to be found in examining the literature! I am not now concerned in determining which set of results is correct, inasmuch as I believe both are valueless, since on the assumption upon which they are based neither can be interpreted.


Long before this sort of comparison was made, however, a voluminous literature arose which was concerned only with the ratio between the carbon dioxid given off and the oxygen consumed, and how this ratio was influenced by temperature, by light, by this kind of food or that, by mere hunger, or by starvation. This ratio, the so-called respiratory ratio or respiratory quotient, the plant physiologists really in- herited from the animal physiologists, by whom it was devised with reference to the gaseous exchange that occurs in the lungs. This respiratory ratio has proved a ver'-


table will-o’-the-wisp, leading investigators into a bog where their labors and _ their thinking were alike futile. For as a sign of what is going on within, the respiratory quotient is absolutely valueless, however interesting the facts in themselves may be. I could cite an indefinite number of in- vestigations to indicate this. I select a few cases,

As long ago as 1885 Rubner showed* that the respiratory ratio varied in resting muscles at different temperatures.


Von Frey and Grubert showed that in a dog’s muscle, with artificial circulation, contractions are accompanied by an in- crease in the earbon dioxid added to the blood, but they found this increase variable (46-10 per cent.) and less than the corre- sponding absorption of orygen, so that the respiratory ratio became lowered during contraction. Tissott showed that the pro- duction of carbon dioxid in exeised mus- cles was increased if the muscle were killed by heat or were fatigued by prolonged stimulation. The output of carbon dioxid in such cases was not related to the rate of absorption of orygen. Six years ago Fletcher.$ Blackman’s apparatus, the most intricate and accurate apparatus vet devised for gaseous eX- changes, showed that the evolution of ear-

using following

**Versuche tiber den Einfluss der Temperatur auf die Respiration des ruhendes Muskels.’ Du- Bois-Reym. Archiv, fiir Physiol. 1885: 38-66.

** Versuche fiber den Stoffwechsel des Muskels.’ DuBois-Reym. Arch fiir Physiol. 1885: 533-562.

t‘ Recherches sur la respiration museulaire,’

Arch. de Phys. norm. et Path. V. 6: 838-844. 1894. Also Variation des echanges gazeux d'un muscle extrait du corps.’ Op. et ser. cit. 7: 641- =1895.

§‘ Survival respiration of Physiol. 23: 10-99. 1898.

muscle.” Jour.


[N.S. Vor. XXI. No. 529.

bon dioxid from excised frog’s muscles is independent of the amount of oxygen taken up during the period. He distinguished in the production of carbon dioxid, first, a short period (about six hours), which he thinks dependent upon the presence of oxy- gen; and second, a long continued evolu- tion of earbon dioxid ‘due to chemical processes occurring spontaneously within the musele, in which complex molecules are replaced by simpler ones, with the con- spicuous results of the appearance of |sar- colaetie| acid and of free carbon dioxid.’ Ile adds: ‘Under suitable conditions the occurrence of active contractions in an ex- cised muscle is not accompanied by an in- crease in the rate at which carbon dioxid is yielded by the muscle,’ though oxygen is abundantly supplied then by the blood. He does find, however, an increased forma- tion of other decomposition products.

Chauveau and Kaufmann, as long ago as 1887, found that the output of carbon dioxid from the levator muscle of a horse’s upper lip was greater during activity than during rest, and contained more oxygen than that absorbed in same time.*

A great number of researches of the same tenor ean be found in botanical lit- erature. A single example must suffice. In an elaborate paper Purjewiez showst that the variations in the earbon dioxid produced and the oxygen absorbed during a given period under various conditions are not parallel, the amount of earbon di- oxid ranging within far wider limits than the oxygen. Thus, the carbon dioxid va- ried from 14 to 120 per cent. of the average; the oxygen varied from 0 to 48 per cent. of the average. Purjewiez, in- deed, expresses his conviction that the res-

** Le coeflicients de l'activité nutritive et respira- toire des muscles.’ Compt. Rend, Acad. Sci. France 104: 1126-1132. 1887.

+* Physiol. Unters. iiber Pflanzenatmung.’ Jahrb. 573-610.

wiss. Bot. 35: 1900.

Fesruary 17, 1905.)

piratory ratio has no value as indicating the actual course of respiration, and would separate the taking up of oxygen and the production of carbon dioxid as two proc- esses only indirectly related.

It is clear that such results as have been cited beeame difficult to reconcile with the idea that respiration is combustion, and so an attempt was made to evade the force of the facts, while maintaining the compari- son, by introducing a qualifying term and speaking of respiration as ‘physiological combustion.” This modification, however, blinks the difficulty ; it does not remove it.

Before passing from this part of my sub- ject I may mention another false concep- tion, which is more or less directly de- pendent on the notion that respiration is combustion. One often finds respiration described as a gaseous exchange—the taking up of oxygen and giving off of carbon di- oxid—a trade between the atmosphere and the body. Clearly this is another case of transferring the superficial interpretation of our own physiological processes to other organisms. The exchange that takes place between the tissues and the blood, between the blood and air in the lungs, gives the foundation, and the unessential phenomena of respiration become substituted for the essential. It would be quite as correct to deseribe photosynthesis as ‘an exchange of vases,’ for carbon dioxid is taken up and oxygen is eliminated. Yet no one ever thinks so superficially of this process.


For three quarters of the last century it was supposed that the evolution of carbon dioxid could only occur when free oxygen was available. But in the early seventies Pfliiger discovered what seemed a peculiar form of respiration. He found that a frog put into a vacuum continued to give off carbon dioxid; and presently the same phenomenon was observed by Pfeffer and



others in plants. So firmly had the con-' ception of combustion fastened itself upon physiologists, that when this anaerobic respiration came to be explained, it was supposed that certain molecules of organic matter within the cell gave up their oxygen to others, that they might thus be burned in the body furnace to yield energy. Hence arose the term intramolecular respiration.

The study of anaerobic respiration, mis- leading as this early interpretation of it was, has thrown in late years a very great light upon normal or aerobic respiration. Here is a process which results in the evolu- tion of energy, and gives rise to one im- portant end-product of aerobic respiration, viz., carbon dioxid; yet it early became evident that it could not be counted a proc- ess of combustion, at least in any sense in which combustion was then understood. Plainly the changes that were going on within the organism which enabled it to give off carbon dioxid when no free oxy- gen was to be had could only be a rear- rangement of atomic groups within the molecule and the formation of products which were simpler than those from which they arose.


The process of fermentation, first thor- oughly explored by Pasteur, whose results have been much extended by the brilliant researches of Hansen and many others, are evidently related to those of respiration by the nature of the end products and the conditions under which the processes occur. Indeed when one compares the end prod- ucts of respiration and of alcoholic fer- mentation he finds them to be identical in all respects. Other sorts of fermentation likewise yield many substances that are found originating in the metabolism of the higher plants.

We have, then, three modes of energy re- lease, which are evidently closely related


if not identical; aerobic respiration, anae- robie respiration and fermentation. Their relations, so far as was known in 1898, were stated by Pfeffer in his * Pflanzen-physiol- ogie’ and need not be reviewed.


In translating that work Ewart wrote (p. 519): **The aetual course of respira- tion within the protoplast is quite obscure.”’ Pfeffer himself says (p. 551) : ‘‘ Our knowl- edge of the inherent protoplastic mechan- ism is too incomplete to afford a sound basis for any theory concerning the phe- nomena of respiration.’’ Fortunately, knowledge in the last six years has broad- ened, and I believe that it is possible now to see pretty clearly what the actual course of respiration is. Perhaps you will say, to foresee rather than to see—but hypothe- sis must outrun demonstration. The ad- vances to which we are indebted for deeper insight are in three fields: (1) the chem- istry of proteids; (2) the course of com- bustion, especially at low temperatures; and (3) the nature of anaerobic respira- tion, and its relation to aerobic respiration. Let me speak of these in order.


A knowledge of the proteids, complex as they are, could only be obtained by a study of their decomposition products. Now there is a very remarkable uniformity in these decomposition products. No matter what the organism from which they are de- rived, no matter how simple they are or how complex, when broken up by the proe- ess of digestion, or by boiling with acids, they vield invariably a series of products which have become in the last few vears much better known. These are amino- or

amido-acids: sueh substanees as leuein,

tvrosin, arginin, glutamin, glycocoll, ete. Materials of this kind are invariably pres- ent, and certain ones are so invariably present that they can be used as the basis


(N.S. Vor. XXI. No. 529.

of distinctive tests for the occurrence of digestion or similar decompositions of pro- teids. This gave a clue to the nature of proteids which was followed by several ob- servers, notably by Kossel, in the study of what are believed to be the very simplest proteids, because of the fewness and uni- formity of the fractions into which they break up. These are the protamines. It has become clear from the study of these simple proteids that they are made up in somewhat the same way as the polysaccha- rides, that is by condensation, in this case linking together a series of the amido- acids. This is possible because the amido- acids have a peculiar construction. They are, so to speak, different on different sides. On one side is an acid group and on the other a basic group; and so the amido-acids can hang together in chains, or even be con- densed or polymerized to make a simple proteid. Among the amido-acids, as in the carbohydrates, there are certain atomic groups, like CH,, CH,, CHOH, CH,OH, COOH, ete., which reeur again and again, and in sueh groups the possibility of re- placing a hydrogen atom or a hydroxy! radicle by some other atomie group is very great.

Note, for instance, the comparatively simple acetie acid, CH, COOH. If we replace one of the three TT atoms by the amido group, NH., we have at once an amido-acid, glyeoeoll, CH,( COOH, which is one of the sorts of material out of which proteids can be made. Out of an alcohol or out of a sugar we may get just the groups CHOH, CH,OH, ete., from which these amido-acids may be construct- ed when nitrogenous substances are present to supply the amido group NH,. Thus the mode of construction of the proteids has been found to show a likeness to that of the complex carbohydrates, and it has long been known that the carbon groups were very much alike in both. It further ap-

FepruaRy 17, 1905.)

pears that when the proteids are digested by any organism they break down into these fragments, of one sort and another, the amido-acids, the amides, ete., which may be put together again in new form to constitute the peculiar proteids of that par- ticular organism. We may thus get one proteid out of any other by the breaking up of the complex molecule and the rear- rangement of its constituent fragments. his fragmentation is readily accomplished hy the proteolytic enzymes, which probably act on these bodies as the diastases do on carbohydrates.


The second important line of progress has been in the study of the oxidation of carbon compounds at low temperatures. For our purpose the important facts which have only recently been developed are that the oxygen of the air does not combine direetly with earbon or with carbon mon- oxide to form CO, or with hydrogen to form H.O, as has heretofore been supposed.

As long ago as 1893 Dixon’s researches* on explosive gases showed that molecular oxygen was by far the most effective of the atmospherie gases in retarding combustion. This surprising result could not be inter- preted then, and only in the light of Traube’s theory and the studies of Bone and others+ on the oxidation of gases like methane and ethane at low temperatures has it been possible to picture the mechan- ism of such combustion. This has been done by Armstrong,t who (with Traube) claims that the substances do not undergo

** The vate of explosion in gases.’ Phil. Trans. Roy. Soc. London A, 184: 97-188. 1893.

+ Bone and Wheeler, ‘The slow oxidation of Trans. Chem. Soc. London 81: 535-545.

1903. Bone and Stockings, Trans. Chem. Soc.

methane.’ 1902; 84: 1074-1087. ‘Slow combustion of ethane.’ London 85: 693-727. 1904.

ft‘ Retardation of combustion by oxygen.’ Chem. Vews 90: 25. 1904. Mechanism of combustion.’ 1903.

Trans. Chem. Soc. London 883: 1088.



direct oxidation, but hydroxylation, 7. e., its hydrogen atoms are successively re- placed by hydroxyl radicles, with conse- quent splitting into various intermediate products, such as earbon monoxid and hydrogen peroxid, carbonic acid and water. being the end products. Armstrong says:

There is little reason to suppose that changes take place at high temperatures in rapid combus- tions in ways very different from those in which they occur at lower temperatures. * * * The effective operation is not the mere blow due to im- pact or the vibration caused by this in the mole- cule, but the conjunction of compatible mole- cules and the consequent formation of composite systems within which change can occur. In so far as temperature influences the formation of compatible systems, either as regards their char- acter or the rate at which they arise, temperature has an influence, but probably not otherwise.

I ask you to notice, then, that the process of combustion is now being interpreted in the light of changes like those which have long been known in organisms under the name of hydrolysis, and are the character- istic mode of action of enzymes. Thus, when starch is acted upon by diastase it is probably by repeated reactions between water, dissociated into hydrogen and hy- droxyl groups, and oxygen, in other words by continued hydroxylation that it becomes ready to fall apart into a series of dextrines and finally into maltose. Diastase in some way facilitates this dissociation. Maltase takes up the task, and maltose, further hydroxylized, cleaves into two molecules of glucose. Then zymase may lend its aid and hydrolyze the glucose molecule into lactic acid, breaking the latter still further into carbon dioxid and alcohol.

The mechanism of the digestion of starch is not known in detail, though the various intermediate products have been fairly well studied. The usual assumption made is merely that water combines with the starch under the action of diastase. I have ear- ried the theory a little further into detail,


as seems warranted by the studies of com- bustion. It is worthy of note also that the late steps in the process, the hydrolysis of glucose by zymase, have been designated by the term fermentation. The combustion of starch has likewise not been examined, but as the end produets are identical with those of digestion, it is not at all improbable that the intermediate steps are the same, though they succeed one another too fast to be fol- lowed by means at present available.

I need hardly remind you that our pres- ent ideas of the dynamies of chemical reac- tions forbid us to believe that such dissoeia- tion does not go on slightly at low tempera- tures, even when unaided. But it slow as to be ordinarily beyond our meas-

is SO

urement, accelerators of the several processes, per- haps preparing ‘compatible systems,’ as high temperature may do in combustion; perhaps entering into union with the sub- stance they act on and forming compounds which are dissociable at ordinary tempera- tures in appreciable amounts.

The clue to an understanding of respira- tion has been found, therefore, not by com- paring it to combustion, which was so long misleading, but by assimilating combustion to respiration. We may hope that chemists will restrict the term combustion or intro- duce a new one that will make more obvious the mode of action. Physiologists at least will do well to drop ‘combustion’ altogether from their vocabulary, as neither the past conception of it nor its probable use in the future conduces to clearness of thought.

The enzymes seem to be mere

NATURE OF ANAEROBIC RESPIRATION, The third line of advance has been in a study of the relations of fermentation and anaerobie respiration. The first step was

that long-sought discovery by Buchner, that the process of fermentation by yeast is brought about by the action of an enzyme which breaks up certain hexose sugars into


[N.S. Von. XXI. No. 529.

carbon dioxid and aleohol. But a fur- ther step in advance has lately been taken. It appears from the work of Buchner and Meisenheimer* that the aleoholie fermenta- tion is not direct, but that it oceurs always in indirect fashion, as shown below.

CHOH CHOH CHOH H CH,OH H bn, H dun, da, oH do OH COOH OH CO, CHOH OHOH H CH,OH CH,OH én, On, glucose water hypo- 2 mols. carbon thetical luctic acid dioxid substance and ethy!


Stépanék has reached the same con- clusion,+ and Mazét has found aeetie acid as an intermediate product in alcoholic fer- mentation by a different yeast.. The in- terest of the discovery that inactive ethy]- idene laetie acid is the intermediate sub- stance in this process of fermentation lies in the facet that one of the two acids of which that is composed, namely, d-ethy]- idene laetie or sareolactie acid, is formed as a product of respiration when proteids break down in the working, fa- tigued, or dying muscle. Fletcher ob- served this as a more prominent product of contracting muscles than carbon dioxid itself. Thus a regular product of fermen- tation is also formed in the ordinary course of respiration.

The analogy between anaerobic respira- tion and fermentation had been suggested early —even by Pasteur—and has thus been growing closer with each added bit of knowledge. But the precise way in which the destruction of the living substance went on in anaecrobie respiration was still un-

**Die chemischen Vorgiinge bei alcoholischen Girung. Ber. Deutsch. Chem. Gesells. 37: 419- 428. 1904.

7+‘ Ueber die aerobe und anaerobe Atmung der Kier.’ Centralbl. Physiol. 18: 188-205. 1904.

t‘ Utilization du carbone ternaire.’ Ann. Inst. Pasteur. 18: 277-303. 1904.

FesRUARY 17, 1905.)

known. Fermentation had been shown to be due to an enzyme. Was anaerobic res- piration also due to an enzyme?

Of course enzymes are known to be pres- ent in a great many of the parts of plants, and the oxidizing enzymes seemed to be the sort to be sought. But none seemed to answer the conditions. At last, however, the object appears to have been attained. Stoklasa, in a series of papers published in various journals* but all dealing with the same general problem, declares he has found in various tissues of animals and in considerable number of plants an enzyme analogous to Buchner’s zymase, and like it glycolytic. This enzyme he reports in leaves and roots of beet, tubers of potato, seeds, seedlings and young plants of pea, seedlings of barley, and entire plants of Paris quadrifolia. Confirmatory results have (naturally enough) been obtained by several students or assistants who have evi- dently been engaged upon portions of the problem under the guidance of Stoklasa. It is only fair to say that Mazé has strongly eriticized Stoklasa’s methods from the bac- teriological side and declares himself un- able to seeure like fermentation under aseptie conditions; though Stoklasa claims to have guarded carefully against infection

*Stoklasa, ‘Identitiit anaerob. Atmung_ u. Giirung. Oesterr. Chem. Zeit. 1903. (Not seen. )

Stoklasa, Jelinek and Vitek, ‘Der anaer.

Stoffwechsel der héh. Pfl. und seine Beziehung z. aleoh. Giirung.’ Beitr. 2. Chem. Physiol. u. Path. 3: 460. 1903.

Stoklasa and Cerny, Isolierung des die anaer.

Atmung der Zelle der héh. org. Pfl. und Tiere bewirk. Enzymes.’ Ber. Deutsch Chem. Gesells. 36: 622-634. 1903. ‘Ueber die anaer. Atm. der Tierorgane u. ueber die Isolierung eines giirungserregenden Enzymes aus dem Tierorganismus.’ Zentralbl. Physiol. 16: 652-658. 1903.

Stoklasa, ‘Ueber die Atmungsenzyme.’ Deutsch, Bot. Geselis. 22: 358-361. 1904.


Various papers in Annales Inst. Pasteur 18: 1904.



and to have rejected contaminated cultures. Independently, Mazé has found what he calls zymase, in connection with pea seed- lings, Aspergillus, and Eurotiopsis. He declares it ‘an enzyme normal to all plants, arising like all the other enzymes during vegetative (aerobic) life.’ In the higher plants, however, and in most fungi it ‘is oxidized with the greatest ease, so that one never finds more than a trace of it.’

Mazé and Stoklasa interpret their results somewhat differently, Mazé holding the process of fermentation to be a nutritive one,* sugar only being assimilable when fermented and the nascent alcohol thus made available, while Stoklasa believes fermentation to be merely anaerobic respi- ration and essentially a process for the immediate release of energy.

Confirmation comes also from another source, for Godlewski,+ working with lupines, finds similar products, and con- cludes that their ‘anaerobic respiration is identical with aleoholie fermentation, or at least in essence dependent on it.’

Moreover Kostytschew{ and Maximow§ have found in Aspergillus an enzyme which is analogous to zymase and is responsible for the formation of CO,, whether in aer- obie or anaerobie respiration.

Thus several independent observers are testifying to the rather widespread occur- rence of an enzyme which brings about a disruption of plant substance, under most varied external conditions, whether the

* ITwanowsky in 1894 propounded the theory that alcoholic fermentation is a pathological case in the nutrition of yeast, called forth by the abnormal composition of the nutritive medium.

+‘ Weiterer Beitr. z. Kennt. der intramol. Atmung.’ Bull. Acad. Sci. Cracovie 1904: 115-158. See also his earlier paper with Polzeniusz, Bull. cit., April, 1901.

t ‘Ueber Atmungsenzyme der Schimmelpilze.’ Ber. Deutsch. Bot. Gesells. 22: 207-215. 1904.

§ ‘Zur Frage tiber die Atmung.’ Ber. Deutsch. Bot. Gesells. 22: 225-235. 1904.


plant be fed on one food or another,* this dissociation resulting in the formation of earbon dioxid and of various other prod- ucts.


Let us now foeus the light coming from the chemistry of proteids, the mechanism of combustion, and the physiology of res- piration, to form a picture of what goes on in the body.

First: We should conceive of the respira- tory dissociation as taking place in the living material of the body and not in a

food still unassimilated. | Experiments with a wide range of foods have shown

that they affect the intake of oxygen and the output of carbon dioxid in the most diverse ways, whence it has been assumed that the respiratory ratio varies because of the way in which the given food is oxidized. I do not say that it is not possible for the protoplasm to decompose a sugar directly or to oxidize a fat. But it must be remem- bered that in no ease has it been experi- mentally proved that the food is directly attacked, and that all the facts can be ex- plained on the other assumption, and some of them very much better than on the theory of direct oxidation. Moreover, the lability of proteids which have been raised to the life-level is their most striking char- acteristic as contrasted with their ordinary stability.

In such labile material the second step is easily conceivable. There occurs a shift- ing of the atomie groups within the mole- cule, perhaps as a result of the last step in their anabolism—the addition of hydroxyl groups from the water everywhere present.

*See a paper by Kostytschew which has just (‘ Veber die normale und die anae- robe Atmung bei Abwesenheit von Zucker’ Jahrb. Wiss. Bot. 40: 563-592. 1904), showing the erroneousness of Diakonow’s idea that anae- robic respiration is only possible when sugar is supplied.

come to hand


[N.S. Vor. XXI. No. 529.

Dissociation follows necessarily; very slow perhaps, at ordinary temperatures and with a seanty supply of water, yet suffic- ient evidently for the maintenance of life. Such conditions may very well be those ob- taining in resting organs, spores and seeds. But normally this cleavage may go on at a measurable rate, without anything more than the inevitable dissociation when hy- droxylation has progressed to a certain point. It seems, however, that there is generally—perhaps always—a hastening of this process, and that the highly unstable protoplasm is dissociated so rapidly that it liberates not only the energy immediately utilized in growth, movement, ete., but also an excess sufficient to be easily meas- ured by so coarse an instrument as the thermometer. Catalytic agents like the enzymes are certainly (I think I may be permitted so strong an assertion) the usual accelerators. And it is highly probable that an enzyme identical with zymase or at least analogous to it, is an active though secondary agent in this acceleration. It may very well be also that those changes outside the protoplast (whether without the organism or not) that are ealled stimuli accelerate still further the katabolism, even to an explosive speed in some cases.

This primary dissociation may plainly be independent of free oxygen, though it is hardly conceivable that there will not be some oxygen present unless the plant has grown under most unusual eonditions, which one ean seareely realize experi- mentally. The products of this decom- position are not sufficiently known, nor is their precise character important for our discussion. Among them are certainly the more complex amido-acids, carbon dioxid and aleohol.

Third: Up to this point the respiratory processes are quite alike whether the plants grow in the air or apart from it. If suffi- cient oxygen be not present the disruptive

Fesruary 17, 1905.]

processes may reach an equilibrium, just as an electrolyte practically ceases to pass a current of electricity unless a depolarizer be present. So in the hydroxylation of proteids, there is needed some substance to disturb constantly, in one direction or an- other, the equilibrium that tends to be reached. The common agent in this is oxygen. Of course oxygen can hardly be the only depolarizer that can promote fur- ther action. Thus, Mazé found the pres- ence of levulose conduced to the continued evolution of carbon dioxid in the absence of oxygen, and it is quite possible that levulose took up the réle of depolarizer, though Mazé does not so interpret his ob- servation.

In anaerobic respiration insufficient oxy- ven is supplied. Its products that have heen most observed and are therefore (though doubtless groundlessly) counted its characteristic products, are carbon di- oxid and aleohol. Indeed, lactic acid seems an equally characteristic though transient produet. The faet that hydrogen has also been often recognized among them supports the interpretation of the function of oxygen just suggested, and accords thoroughly with the theory of hydroxylation. In that proce- ess hydrogen atoms from the dissociation of water would be left free in case there was insufficient oxygen to form H,O,,.

Fourth: But if the organism can get an

adequate supply of oxygen, the katabolism:

continues, some of the most complex pre- vious products breaking up by hydroxyla- tion and thermal cleavage. Among the fragments are undoubtedly some that lose in part those very groups in which sugars, aleohols, fatty acids, ete., are peculiarly rich. These are rebuilt at the expense of such foods, which therefore disappear as a result of respiration. That ethyl aleohol does not persist when oxygen is present may mean either that it is decomposed, or that in its nascent state it is assimilated in



the rebuilding of proteids, for we have seen how easily acetic acid, one of its oxidation products, can be converted into an amido- acid, glycocoll, and be thus in direct line for reconstructive metabolism.

This in its fundamental features is the theory I have presented in lectures to ad- vanced students since 1898, though always as more or less a speculation. For various details I am indebted to the recent litera- ture already cited. Because it is capable of explaining the observed facts, which are sufficiently numerous to demand a coherent explanation, I conceive it to be entitled to the dignity of a theory. Time forbids the discussion of details, and many points have been considered that can not be here pre- sented.

This theory maintains the direct relation of aerobie and anaerobic respiration, whose genetic connection was long since advocated by Pfeffer. Anaerobic respiration is the primary process in all organisms. Whether aerobie respiration occurs or not depends upon the availability of oxygen. The rela- tion of fermentation to the process is not wholly clear; for although fermentation gives rise to the same products as anaerobic respiration, this may depend in part upon respiratory decomposition, such as has been described, and in part upon digestion, which, as Iwanowsky and Mazé think, ren- der the aleohol from sugars available for assimilation. I am inclined to believe that in fermentation we deal with an exag- gerated anaerobic respiration, the active ferments being plants in which zymase is produced in such amounts that it ean at- tack sugars outside the organism and thus secure sufficient energy with a minimum destruction of the protoplasm.

ENERGESIS. Finally, I may suggest that for didactic purposes it is desirable to have a word other than respiration to designate the disruptive


processes by which energy is released, leav- ing respiration to designate the more super- ficial phenomena of aeration with which plant physiologists are little concerned. Perhaps the word respiration is already too firmly imbedded in literature to be so limited. It will at least do no harm to propose that the terms aerobic and anaer- obie energesis be considered, to which fer- mentative energesis may be added if neces- sary. CHARLES R. BARNES. THe UNIVERSITY OF CHICAGO.


Tue meetings were held in the John Harrison Laboratory of Chemistry of the University of Pennsylvania, with the ex- ception