562 Proceedings of the British Association. 



complaints. But when they are removed to warmer climates, they absorb 

 less oxygen, and take less food ; and the diseased organs of digestion have 

 sufficient power to place the diminished amount of food in- equilibrium 

 with the respired oxygen. Just as we would expect from these views, in 

 our own climate, hepatic diseases or diseases arising from excess of 

 carbon, are more prevalent in summer, and in winter pulmonic diseases, 

 or those arising from an excess of oxygen. The Professor then went on 

 to disprove the notion, that animal heat is due to nervous influence, and 

 not to combustion — an error which had its origin in supposing that the 

 combustion proceeds in the blood itself. He also shewed, that animal 

 heat must not be ascribed to the contraction of the muscles. The Pro- 

 fessor proceeds to prove, that the heat evolved by the combustion of 

 carbon in the body is sufficient to account for the phenomena of animal 

 heat. He shews that the 14 ounces of carbon which are daily convert- 

 ed into carbonic acid, in an adult, disengage no less than 197.477° of 

 heat ; a quantity which would convert 241b. of water, at the temperature 

 of the body, into vapour. And if we assume that the quantity of water 

 vaporized through the skin and lungs amounts to 3lb., then we have 

 still 146.380° of heat to sustain the temperature of the body. And 

 when we take into calculation the heat evolved by the hydrogen of the 

 food, and the small specific heat possessed by the organs generally, no 

 doubt could be entertained that the heat evolved in the process of com- 

 bustion, to which the food is subjected in the body, is amply sufficient 

 to explain the constant temperature of the body. From what has pre- 

 ceded, it is obvious that the amount of carbon consumed in food ought 

 to depend on the climate, density of air, and occupation of the indivi- 

 dual. A man will require less carbon when pursuing a sedentary occupa- 

 tion than when he is engaged in active exercise. Prof. Liebig, having 

 thus discussed the source of animal heat, proceeds next to consider what 

 are the ingredients in the food, which may properly be considered to be 

 nutritious. Physiologists conceive that the various organs in the body 

 have originally been formed from blood. If this be admitted, it is 

 obvious that those substances only can be considered as nutritious which 

 are susceptible of being transformed into blood. The Professor then 

 entered upon an examination of the composition of blood, and of the 

 identity in chemical constitution of fibrine and albumen. The nutritive 

 process is simplest in the case of the carnivora. This class of animals 

 live on the blood and flesh of the graminivora, whose blood and flesh is 

 identical with their own. In a chemical sense, therefore, a carnivorous 

 animal, in taking food, feeds upon itself: for the nutriment is identical 

 in composition with its own tissues. The Professor then inquired 



