156 TEMPERATURE OF THE BLOOD. 



on the quantity and quality of the food", the state of the system, &,e. 

 Something less than this is the probable average. It is also thought 

 that the skin effects changes of the air not unlike those produced by 

 the lungs. 



The combination of carbon with oxygen thus, or in aay way effected 

 in the system, evolves heat. Thus a pound of pure charcoal, by 

 combination with oxygen gas, evolves heat sufficient to elevate the 

 temperature of 78 pounds of water from 32 to 212 Fahr. This, then, 

 Is supposed to be the source of animal heat, indispensable to the vita) 

 process. The conversion of sugar or starch into fat, supplies the 

 system with oxygen, and heat is developed by the union of this 

 with carbon, as with the bile, &c. Whilst the animal system is in a 

 healthy condition, the necessary carbon for the supply of heat is fur- 

 nished by the food, but otherwise and without food, the fat of the body 

 is consumed by its carbon being converted into carbonic acid and it 

 bydiogen into water. 



Diseases of the liver, so frequent in hot seasons and climates, is as- 

 cribed by Liebig to an accumulation of carbon in the body. Hep- 

 atic diseases arising from an excess of carbon, are prevalent in summer, 

 while in winter pulmonary diseases are frequent, in consequence of an 

 excess of oxygen. The system requires less carbonaceous food and less 

 in quantity in warm than in cold weather j and hepatic diseases among 

 people from the north, residents of tropical climates, is attributed to 

 the use of food fitted only for their former residence and climate. The 

 size of the liver is thought to be inversely in proportion to that of the 

 respiratory organs. Carbonic acid is evolved in proportion to the 

 temperature, the lungs being inefficient when the air is much rar- 

 ified ; consequently the liver must excrete more carbon to preserve 

 the blood from carbonaceous matter ; and a greater secretion of bile is- 

 required in hot climates to compensate for the lesser action of the 

 lungs in purifying the blood. Less carbonic acid is evolved by per- 

 sons living on vegetable diet than when living on animal food. 



The heat of the blood being the same in all climates and conditions, 

 a, larger portion of combustible materials is required to preserve the 

 necessary temperature in cold than in warm weather, because more 

 heat is given off to surrounding objects, having less of it ; conse- 

 quently more food is required. It is, indeed, generally known that a 

 person well supplied with nutritive food in cold weather sustains the 

 cold much better than one sparingly supplied, and that a person will 

 die much sooner without food in cold than in warm weather. Hence 

 the enormous quantity of food consumed by people in very cold lati- 

 tudes, and the small quantities consumed by those in very warm cli- 

 mates. The customary food also of the first is seen to be chiefly fats 

 and oils, containing from 66 to 79 per cent, of carbon, while that of 

 the latter (the Hindoos for example) is a light vegetable food. An 



