ANIMAL, HEAT. 265 



while traversing the organ, to 40 per cent, of its original quantity. But 

 when the gland is excited to active secretion, its circulation is increased 

 in rapidity, and its venous blood more abundant and brighter in color - r 

 its oxygen being only reduced to 61 per cent, of that in arterial blood.. 

 At the same time the temperature of the gland rises, notwithstanding 

 that its consumption of oxygen is less than in a condition of repose. 



A similar elevation of temperature takes place in the blood while 

 traversing the capillary circulation of the intestine and of the liver. 

 The following tables give the results of two series of observations by 

 Bernard on the temperature of the blood entering and leaving these 

 organs in the dog : 



TEMPERATURE OF THE BLOOD ix THE 

 Aorta. Portal Vein. 



36.8 38.8 



40.3 40.7 



39.4 39.5 



Portal Vein. Hepatic Vein. 

 40.2 40.6 



40.6 40,9 



40.7 40.9 



Thus the blood of the hepatic vein, after traversing two successive 

 capillary circulations, is warmer than that in any other part of the 

 body. 



Even in the kidneys, when the secretion. of urine is active, there is a 

 rise of temperature in the blood of the rena 1 ! veins. At the same time, 

 as in the submaxillary glands, the circulation is increased, the venous 

 blood leaves the organ of a bright red color, and its proportion of 

 oxygen, according to Bernard, is only reduced to 88 per cent, of that 

 contained in the arteries, while in the condition of glandular repose it 

 is reduced to 33 per cent. 



It is evident, therefore, that animal heat may be derived from other 

 causes than the immediate consumption of oxygen and formation of 

 carbonic acid. Even outside the body heat may be produced by the 

 hydration of quick-lime, or by the mixture of water with alcohol or 

 sulphuric acid ; and the changes of nutrition, consisting largely of 

 hydrations, and other chemical or physical actions in which direct oxi- 

 dation does not take part, are sufficient to account for the heat-produc- 

 tion within the living frame. This heat-production is a local process, 

 and takes place with different degrees of intensity according to special 

 acts of nutrition in different organs. In the muscles it is accompanied 

 by increased consumption of oxygen and deeper coloration of the 

 venous blood ; in the salivary glands and the kidneys by diminished 

 consumption of oxygen and a less complete change in the color of the 

 blood. The temperature of the blood coming from each organ is in 

 proportion to the activity of heat-production in the organ itself; that 

 of the venous blood consequently varies in different parts, while that 

 of arterial blood is everywhere sensibly the same. 



