3 86 TEXT-BOOK OF PHYSIOLOGY. 



as their temperature is inconstant, varying with the temperature of 

 the surrounding medium, they are more appropriately termed "varia- 

 ble temperatured " or poikilo-thermous animals. 



THE TEMPERATURE OF THE HUMAN BODY. 



The determination of the temperature of the human body under 

 the changing conditions of life is a matter of the greatest physiologic 

 and clinical interest. The temperature of the superficial portions of 

 the body may be obtained by the introduction of a thermometer into 

 the mouth, the rectum, the vagina, or the axilla. As a result of many 

 observations it has been found that the temperature of the rectum is, 

 on the average, 37.2 C.; that of the mouth, 36.8 C.; that of the 

 axilla, 36.9 C. Owing to radiation and conduction the surface tem- 

 perature is lower than that of either the mouth or rectum, and varies 

 to a slight extent in different regions of the body: e. g., at a room- 

 temperature of 20 C. the skin of the pectoral region has a tem- 

 perature of 34.7; that of the cheek, 34.4; that of the calf, 33.6; 

 that of the tip of the ear, only 28.8, etc. 



In the interior of the body, especially in organs in which oxidation 

 takes place rapidly, and which at the same time are protected by 

 their anatomic surroundings from rapid radiation, the temperature 

 is higher than that observed in the rectum. From an investigation 

 of the temperature of the blood as it emerges from the liver, the 

 muscles, the brain, alimentary canal etc., it is evident that these 

 organs have a higher temperature than the rectum. 



As the chemic changes underlying physiologic activity vary in 

 intensity and extent in different regions of the body, there would be 

 marked variations in their temperature were it not that the blood, 

 having a large capacity for heat-absorption, distributes the heat 

 almost uniformly to all portions of the body, so that at a short distance 

 beneath the surface the temperature does not vary but within a few 

 degrees. 



In the dog the temperature of the blood in the aorta and in its 

 principal branches is approximately 38.3 C. In passing through 

 the systemic capillaries the temperature falls from radiation and con- 

 duction to surface temperature, to again rise as the venous blood 

 approaches the deeper regions of the body. In the neighborhood 

 of the renal veins and in the superior vena cava the temperature is 

 again that of the aorta. In the portal vein the temperature rises to 

 40.2 C. ; in the hepatic vein, to 40.6 C. In the right ventricle, owing 

 to the admixture of blood from different localities having different 

 temperatures, the temperature falls to 38.2 to 40.4. In passing 

 through the pulmonary capillaries the temperature of the blood again 

 falls, so that in the left ventricle it will register from 38 C. to 40.2 C. 



