ADDRESS. 2 1 



greater interest, nor, I may add, of greater complexity, than that which, 

 bearing on the vital functions both of plants and of animals, endeavours 

 to unravel the tangled skein of the chemistry of life, and to explain the 

 principles according to which our bodies live, and move, and have their 

 being. If, therefore, in the less complicated problems with which other 

 portions of our science have to deal, we find ourselves, as we have seen, 

 often far from possessing satisfactoiy solutions, we cannot be surprised to 

 learn that with regard to the chemistry of the living body — whether 

 vegetable or animal — in health or disease we are still farther from a 

 complete knowledge of phenomena, even those of fundamental importance. 



It is of interest here to recall the fact that nearly fifty years ago 

 Liebig presented to the Chemical Section of this Association a com- 

 munication in which, for the first time, an attempt was made to explain 

 the phenomena of life on chemical and physical lines, for in this paper he 

 admits the applicability of the great principle of the conservation of 

 energy to the functions of animals, pointing out that the animal cannot 

 generate more heat than is produced by the combustion of the carbon 

 and hydrogen of his food. 



' The source of animal heat,' says Liebig, ' has previously been 

 ascribed to nervous action or to the contraction of the muscles, or even 

 to the mechanical motions of the body, as if these motions could exist 

 without an expenditure of force [equal to that] consumed in producing 

 them.' Again he compares the living body to a laboratory furnace in 

 which a complicated series of changes occur in the fuel, but in which the 

 end-products are carbonic acid and water, the amount of heat evolved 

 being dependent, not upon the intermediate, but upon the final products. 

 Liebig asked himself the question, does every kind of food go to the 

 production of heat ; or can we distinguish, on the one hand, between the 

 kind of food which goes to create warmth, and, on the other, that by 

 the oxidation of which the motions and mechanical energy of the body 

 are kept up ? He thought that he was able to do this, and he divided 

 food into two categories ; the starchy or carbohydrate food is that, said 

 he, which by its combustion provides the warmth necessary for the 

 existence and life of the body. The albuminous or nitrogenous constituents 

 of our food, the flesh meat, the gluten, the casein out of which our 

 muscles are built up, are not available for the purposes of creating 

 warmth, but it is by the waste of those muscles that the mechanical 

 energy, the activity, the motions of the animal are supplied. We see, 

 said Liebig, that the Esquimaux feeds on fat and tallow, and this 

 burning in his body keeps out the cold. The Gaucho, riding on the 

 pampas, lives entirely on dried meat, and the rowing man and pugilist, 

 trained on beefsteaks and porter, require little food to keep up the tem- 

 perature of their bodies, but much to enable them to meet the demand 

 for fresh muscular tissue, and for this purpose they need to live on a 

 strongly nitrogenous diet. 



Thus far Liebig. Now let us turn to the present state of our know- 



