512 REPOKT— 1880. 



transformations, other than those coming under either of the heads iu question, in 

 illustration of his subject ; and he discussed with great clearness the ditterent con- 

 ditions occurring, and the different results obtained, in various processes — such as 

 the diiferent modes of fermenting beer, the fermentation of wme from different 

 kinds of grapes, the production of acetic acid, &c. As is well known, he claimed 

 a purely chemical explanation for the phenomena involved in fermentation. He 

 further maintained that the action of contagions was precisely similar. In his latest 

 writings on the subject (in 1870), he admits some change of view: but it is by no 

 means easy to decide exactly how much or how little of modification he would wish 

 to imply. 



Liebig's second report, presented at the meeting of this Association in 1842, 

 and published under the title of ' Animal Chemistry, or Organic Chemistry in its 

 applications to Physiology and Pathology,' perhaps excited even more attention than 

 his first, and, probably fi-om the manner as much as from the matter, aroused a great 

 deal of controversy, especially among physiologists and physicians. Liebig was 

 severe upon what he considered to be a too exclusive attention to morphological 

 charactei-s in physiological research, and at any rate too little attention to chemical 

 phenomena, and, so far as these were investigated, an inadequate treatment of the 

 subject according to strictly quantitative methods. 



He combated the view that nervous action, as such, could be a source of any 

 of the heat of the body ; and he adduced numerous illustrations and calculations 

 in support of the view that the combustion of carbon and h^-drogen in the system 

 was sufficient to account for, and was the only source of, animal heat. 



He compared and contrasted the general composition of plants and animals. 

 In accordance with Mulder, he pointed out that whilst plants formed the nitro- 

 genous bodies which they contain from carbonic acid, water, and ammonia, animals 

 did not produce them, but received them readj'-formed in their vegetable food ; 

 that, in fact, the animal begins only where the plant ends. But, going beyond 

 Mulder, and beyond what had then, or has since, been established, he maintained the 

 identity in composition of the admittedly analogous nitrogenous compounds in plants 

 and in the blood of animals. 



Omitting the fat which the carnivora might receive in the animals they con- 

 sumed, he stated the characteristic difference between the food of carnivora and 

 herbivora to be, that the former obtained the main proportion of their respiratory 

 material from the waste of tissue ; whilst the latter obtained a large amount from 

 starch, sugar, itc. These different conditions of life accoimted for the comparative 

 leanness of carnivora and fatness of herbivora. 



He maintained that the vegetable food consumed by herbivora did not contain 

 anything like the amount of fat which they stored up in their bodies ; and he 

 showed how nearly the composition of fat was obtained by the simple elimination 

 of so much oxygen, or of oxygen and a little carbonic acid, from the various carbo- 

 hydrates. Much less oxygen would be required to be eliminated from a quantity 

 of fibrine, &c., containing a given amount of carbon, than from a quantity of carbo- 

 hydrates containing an equal amount of carbon. The formation of fatty matter in 

 plants was of the same kind ; it was the result of a secondary action, starch being 

 first formed from carbonic acid and water. 



He concluded from the facts adduced that the food of man might be di\ided 

 into the nifrogenised and the non-nitrogenised elements. The former were capable of 

 conversion into blood, the latter incapable of such transformation . The former might 

 be called the p^ffs^ic elements of nuti-ition, the latter elements of resjn)-af ion. From 

 the plastic elements, the membranes and cellular tissue, the nerves and brain, car- 

 tilage, and the organic part of bones, could be formed ; but the plastic substance 

 must be received ready-made. "Whilst gelatine or chondrine was derived from 

 fibrine or albumen, fibrine or albumen could not be reproduced from gelatine or 

 chondrine. The gelatinous tissues suffer progressive alteration under the influence 

 of oxygen, and the materials for their re-formation must be restored from the blood. 

 It might, however, be a question whether gelatine taken in food might not again 

 be converted into cellular tissue, membrane, and cartilage, in the body. 



At that time, adopting and attaching great importance to Mulder's views in 



