ANIMAL HEAT. 401 



to the comparative temperature 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 ; while others suppose that 

 the blood is slightly refrigerated in the air-cells. The ques- 

 tions here involved will be fully discussed in connection with 

 the theories of animal heat ; and we shall confine ourselves 

 at present to a study of the experimental facts. 



An excellent review of all the important direct observa- 

 tions upon the temperature of the two sides of the heart in 

 living animals is given by Bernard, as an introduction to his 

 original experiments. It appears from this that Golem an, 

 Astley Cooper, Saissy, Davy, Thackrah, and Nasse, found 

 the blood warmer in the left side of the heart than in the 

 right. Mayer did not find any difference in animals re- 

 cently killed. Autenreith found the blood warmer in the 

 right side in an animal recently killed, the circulation being 

 kept up by artificial respiration. Berger, Collard de Mar- 

 tigny, Magendie and Bernard, Hering, Georg von Liebig, 

 and Fick found a marked difference in favor of the right 

 side. 1 This being the state of the question in 1859, it re- 

 mains to see how far the conditions under which these re- 

 sults were obtained are capable of explaining their contra- 

 dictory character. 



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 observations made in this way, and depend en- 

 tirely upon experiments in which the physiological condi- 

 tions are not so palpably violated. Magendie and Bernard 

 introduced delicate thermometers into the two sides of the 



1 BERNARD, Liquides de Vorganisme, Paris, 1859, tome i., p. 55, el seq. 



