TEMPERATURE OF THE BLOOD AND TISSUES. 



431 



Blood of the right heart, . 



left 

 ,, aorta, 

 ,, hepatic veins, 



,, superior vena cava, 

 ,, inferior ,, 



,, crural vein, 



38-8 



38 -6 



38-7 



39-7 



36-78 



38-11 



37-20 



Cl. Bernard. 



v. Liebig. 



The lower temperature of the blood in the left heart may be explained by the 

 blood becoming cooled in its passage through the lungs during respiration. 

 According to Heidenhain and Korner, the right heart is slightly warmer because 

 it lies in relation with the warm liver, whilst the left heart is surrounded by the 

 lung which contains air. This observation of Malgaigne (1832), Berger, and 

 G. v. Liebig is disputed by others, who say that the left heart is slightly warmer 

 (Jacobson and Bernhardt) because the combustion processes are more active in 

 arterial blood, and heat is evolved during the formation of oxyhoemoglobin 

 (Gamgee). The blood in the veins is usually cooler than in the corresponding 

 arteries (Haller), owing to the superficial position of the former, whereby they 

 give off heat during their long course; thus the blood of the jugular vein is 5 to 

 2C. lower than the blood in the carotid (Colin); the crural vein f-l cooler than in 

 the crural artery (Becquerel and Brechet). Superficial veins, more especially those 

 of the skin, give off much heat, and their blood is, therefore, somewhat cooler. 

 The ^oarmcst blood is that of the hepatic vein, 39-7C. (Cl. Bernard), partly owing 

 to the great chemical changes which occur within the liver (p. 432), and partly 

 to its protected situation. By means of small outflow thermometers introduced 

 into the circulation, Kronecker and Meyer found the following temperatures in 

 three starving dogs: Vena azygos, 37'7 (38'0) (39'0); right ventricle, 38 '3 (39-2) 

 (39'2); branch of the pulmonary artery, 38'4 (38'6) (40'2). At the same time, the 

 temperature in the stomach was 38 '6 (37 '3) (40 -0), and in the rectum, 39 -5 (39 '5) 

 (39*4); the maximum temperature in the last two dogs was 40'1 and 41 '2, hence 

 in the starving condition, the temperature of the stomach was less than the 

 tempei-ature of the blood in the pulmonary circulation. 



4. Temperature of the Tissues. The individual tissues are warmer: 

 (1) the greater the transformation of kinetic energy into heat 3 i.e., the 

 greater the tissue metabolism; (2) the more blood they contain; (3) 

 and the more protected their situation. According to Heideuhaiu and 

 Korner, the cerebrum is the warmest organ in the body. 



Berger measured the temperature of the tissues of a sheep, and found the 

 following: 



Subcutaneous tissue, . 37 "35 



Brain, . . . 40 '25 



Liver, . . . 41 -25 



Lungs, . . . 4T40 



While the temperature was in 

 Rectum, . . . 40 '67 

 Eight heart, . 41 -60 



Left heart, . 40 "90 



Becquerel and Brechet found the temperature of the human subcutaneous tissue 

 to be 2'1C. lower than that of the neighbouring muscles. The horny tissues do 

 not produce heat, and their low temperature is due to the conduction of heat from 

 the parts on which they grow. The temperature of the cornea partly depends on 

 that of the iris, and the more contracted the pupil is, it receives more heat from 

 the blood-vessels of the iris. 



