ANIMAL HEAT. 399 



tastatic " thermometers of M. "Walferdin ; 1 and in all com- 

 parative observations lie employed the same instrument, in- 

 troduced successively into different parts, frequently revers- 

 ing the order, and employing every precaution so as to insure 

 perfectly physiological conditions. The preeminent skill of 

 this distinguished observer in experimenting upon living ani- 

 mals is almost in itself a sufficient guarantee of the accuracy 

 of his results. 



It is universally admitted that the blood becomes slightly 

 lowered in its temperature in passing through the general 

 capillary circulation ; 3 but the amount of difference is ordi- 

 narily not more than a fraction of a degree, and is dependent, 

 in all probability, upon external conditions and the evapora- 

 tion constantly going on from the surface of the body. This 

 fact is not at all opposed to the proposition that the animal heat 

 is generated in greatest part in the general capillary system, 

 as one of the results of nutritive action ; for the blood circu- 

 lates with such rapidity that the heat acquired in the capil- 

 laries of the internal organs, where little or none is lost, is 

 but slightly diminished before the fluid passes into the arte- 

 ries, even in circulating through the lungs ; and the evapora- 

 tion from the surface simply moderates the heat acquired in 

 the tissues, and keeps it at the proper standard. We know 

 that the heat of the body is equalized by means of the circu- 

 lation and cutaneous transpiration ; and all comparative ob- 

 servations on the temperature in different parts show that, 

 where it is not subjected to refrigerating influences, the blood 

 is warmer in the veins than in the arteries. 



The elaborate investigations of Bernard have demon- 

 strated that the blood is, as the rule, from 0'36 to 1-8 

 warmer in the hepatic veins than in the aorta. The tem- 

 perature in the hepatic veins is from 0*18 to 1*44 higher 



1 BERNARD, Liquides de Forganisme, Paris, 1859, tome i., p. 67, et seq. Ber- 

 nard here gives a full description of this instrument. With it he has been able 

 to note accurately variations of ^ of a degree cent. 



8 BERNARD, op. cit., p. 58, and LOXGET, Traite de phyeioloffie, Paris, 1869, tome 

 ii., p. 517. 



