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VIII. Food in its relations to various exigencies of the Animal 

 Body. By J. B. Lawes, F.R.S., F.C.S., and J. H. Gilbert, 

 Ph.D., F.R.S., F.C.S* 



THE appearance in the June (Supplementary) Number of the 

 Philosophical Magazine of the interesting paper by Profes- 

 sors Pick and Wislicenus "On the Origin of Muscular Power," and 

 the further interest excited in the subject by Professor Frankland' s 

 recent lecture at the Royal. Institution, seem to render it oppor- 

 tune that the important question of the connexion between certain 

 constituents of food and certain exigencies of the animal body 

 should receive a little further consideration at the present time. 

 Professor Frankland truly said that, since the appearance of Baron 

 Liebig's masterly and highly suggestive work ( On Organic Che- 

 mistry in its applications to Physiology and Pathology " in 1842, 

 his views of the relation of the nitrogenous and the non-nitro- 

 genous constituents of food to certain requirements of the ani- 

 mal organism have been pretty generally adopted by text-book 

 writers. It is also true that authorities on the subject of the 

 chemistry of food have, even so recently as last year and this, 

 either directly maintained or taken for granted the correctness 

 of Baron Liebig's views. It is, however, not the case, as was 

 also assumed by Professor Frankland, that those views have re- 

 mained unquestioned excepting in the one or two instances of 

 criticism to which he referred. 



This question, in various aspects, has occupied a great deal 

 of our own attention for many years past ; and so loag ago as 

 1852 we advocated substantially the views now adopted by Pro- 

 fessors Fick, Wislicenus, and Frankland ; and we have on various 

 occasions since that date expressed them with greater definiteness, 

 and urged them the more emphatically, as new experimental evi- 

 dence either of others or ourselves seemed to lend them support 

 or confirmation. It may be well, therefore, to state very briefly 

 the course of our own investigations bearing upon the subject, 

 and also the conclusions that we have based upon them. 



In Baron Liebig's work above alluded to, and also in subse- 

 quent publications, he treated of the food requirements of the 

 animal body generally — that is, under different conditions ; and 

 starting from the fundamental assumptions, on the one hand, of 

 the direct connexion of the nitrogenous or, as he designated 

 them, the "plastic " constituents of food, not only with the for- 

 mation in the animal body of the compounds containing nitrogen, 

 but also with the development of muscular power, and, on the 

 other, of the general relationship of the non-nitrogenous con- 

 stituents of food with respiration, the development of heat, and 



* Communicated by the Authors. 



