ANIMAL HEAT 443 



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 observa- 

 tions it has been found that the temperature of the rectum is, on 

 the average, 37.2C.; that the mouth, 36.8C.; that of the axilla, 36.9C. 

 Owing to radiation and conduction, the surface temperature 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 2oC. 

 the skin of the pectoral region has a temperature 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. 



FIG. 199. SCHEME TO SHOW THE TOPOGRAPHIC DISTRIBUTION OF THE TEMPERATURE IN 

 THE LARGE BLOOD-VESSELS. - The degree of temperature in these vessels is expressed at each 

 point by its height above a conventional abscissa which is here the aorta, in which the tem- 

 perature is practically uniform. (After Bernard.') 



As the chemic changes underlying physiologic activity vary in intensity 

 and extent in different regions of the body, there would be marked varia- 

 tions 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 varies but a few degrees. 



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

 branches is approximately 38.6C. In passing through the systemic cap- 

 illaries the temperature falls from radiation and conduction to surface 

 temperature, to again rise as the venous blood approaches the deeper regions 

 of the body (Fig. 199). 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 39C.; in the hepatic vein, to 39.7C. 

 In the right ventricle, owing to the admixture of blood from different 

 localities having different temperatures, the temperature falls to 38. 8C. In 

 passing through the pulmonic capillaries the temperature of the blood again 

 falls, so that in the left ventricle it will register 38.6C. There is thus 

 usually a difference between the two sides of the heart of about o.2C. 



