242 



SCIENCE. 



[N. S. Vol. XXI. Xo. 529. 



this disappearance cf oxygen and forma- 

 tion of carbon dioxide are only the external 

 indication of respiration, as has been long 

 recognized. 



RESPIRATION IN ANIMALS. 



Upon undertaking- a special consideration 

 of this topic, I found it needful to examine 

 the recent literature of 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 physiologists have concerned them- 

 selves very little with the essential prt)l)- 

 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 inti'ieate struc- 

 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- 

 tion for the voluntary and involuntary 

 movements which it executes ; the blood, 

 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 those it gives up to the tissues— 

 these are the topics 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 Physi(!lrgy' and 

 Schaefer's ' Text-book of Physiology,' but 

 in them I found no treatment whatever, 

 indeed no mention whatever, of the real 

 problems of resj)iration, that is, of 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 clue to the literature 



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. I am intending, however, neither ar- 

 raignment nor excuse, but a bare statement 

 of what were to me rather surprising facts. 



RESPIRATION IN PLANTS. 



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 

 chemistiy 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 years after his 

 time. In 1804 DeSaussure showed that 

 growth is dependent on respiration : that 

 respiration is more active in groAving parts 

 than elsewhere ; that it is the cause of the 

 loss of weight to Avhich 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- 

 trocliet 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 the 

 confusion that arose between respiration 

 and the manufacture of carbohydrates, 

 which Dutroehet called 'diurnal respira- 

 tion.' Of that I shall not speak, save to 

 say that the great weight of Liebig's au- 

 thoi'ity made this error persist for half a 

 centui'y. 



RESPIRATION AND COMBUSTION. 



The other misconception was engendered 

 by the comparison of respiration to com- 



