ANIMAL HEAT. 507 



The investigations of Bernard have demonstrated that the hlood is, as a rule, from 

 0'36 to 1'8 warmer in the hepatic veins than in the aorta. The temperature in the he- 

 patic veins is from 0'18 to 1'44 higher than in the portal veins. These figures are the 

 result of many experiments made upon dogs. Compared with the aorta, the temperature 

 in the portal vein was generally found to be higher (maximum of difference, 0'9) ; but, in 

 a few instances (five out of fifteen), it was a very little lower, which is explained by Ber- 

 nard upon the supposition that the intestinal canal is not entirely removed from external 

 modifying influences. These results show that the blood coming from the liver is warmer 

 than in any other part of the body. In a series of experiments by Breschet and Becquerel, 

 who were among the first to employ thermo-electric apparatus in the study of animal 

 heat, it was found that the cellular tissue was from 2'5 to 3'3 cooler than the muscles. 



A most interesting question, in this connection, relates to the comparative tempera- 

 ture of the blood in the two sides of the heart. Upon this point there have been several 

 conflicting observations, the results favoring two opposite theories of calorification. By 

 some it has been thought that the blood gains heat in passing through the lungs, and this 

 is explained by the theory of the direct union, in these organs, of oxygen with the 

 hydro-carbons. Others suppose that the blood is slightly refrigerated in the air-cells. 



It is evident that, when the chest is opened, the external refrigerating influences 

 might act differently upon the two sides of the heart, particularly as the right ventricle 

 is much thinner than the left. It would not be improper, indeed, to exclude all observa- 

 tions made in this way, and to depend entirely upon experiments in which the physiological 

 conditions are not so palpably violated. Magendie and Bernard introduced delicate ther- 

 mometers into the two sides of the heart, through the vessels in the neck, without opening 

 the chest. These experiments were made upon a horse, and the right heart was always 

 found considerably warmer than the left. Bering introduced a thermometer into the cavi- 

 ties of the heart in a living calf affected with cardiac ectopia. The temperature of the 

 right side was 102'74: , and the left side, 101'79. Georg von Liebig illustrated one of 

 the sources of error in all examinations made after opening the chest, by filling the cavi- 

 ties of the heart of a dog with warm water, placing the organ in a water-bath, and bring- 

 ing the two sides to precisely the same temperature. After five minutes' exposure to the 

 air, the temperature in the right ventricle was sensibly lower than in the left, whirh 

 was undoubtedly due to the difference in the thickness of the ventricular walls. The 

 observations made by Bernard upon dogs and sheep are very conclusive, as far as 

 these animals are concerned. In dogs he found a difference of from 0*1 to 0'2, 

 always in favor of the right side; and the results in sheep were nearly the same. 

 These experiments are only indirectly applicable to the human subject ; and if it be 

 proven that, in animals, the conditions vary with " the state of the skin, the digestive 

 apparatus, and the muscular system " (Colin), it is impossible, in the absence of positive 

 demonstration, to say what change in temperature, if any, takes place in the blood in its 

 passage through the lungs. The only reliable observations upon this point in man are 

 those made by Prof. J. S. Lombard, who used a very ingenious and delicate thermo- 

 electric apparatus capable of indicating a difference of ^Vfr f a degree cent. With this 

 instrument, he was able to determine very slight variations in the temperature of the 

 blood in the arterial system, by simply placing the conductors over any of the superficial 

 vessels, like the radial. Of course it is impossible to note the actual temperature in the 

 two sides of the heart in the human subject during life ; but Prof. Lombard endeavored 

 to arrive at the same end, by calculating that, if all the sources of refrigeration in the 

 lungs were artificially removed, the blood in the arteries should gain about the same 

 amount of heat that would be lost under ordinary conditions. To effect this object, ho 

 breathed air saturated with moisture and of the same temperature as the circulating 

 blood. " If, then, when respiration takes place under ordinary circumstances, the blood 

 is cooled one-third of a degree (cent.) in passing through the lungs, the temperature 

 nhould be raised so much ; that is to say, one-third of a degree, when we respire air at the 



