ANIMAL HEAT. 61 



ratory muscles, attended by convulsions of the muscles of the extremities, 

 engorgement of the venous system, lividity of the skin, abolition of sensi- 

 bility and reflex action, and death. 



The cause of death is a paralysis of the heart, from over distention by 

 blood. The passage of the blood through the capillaries is prevented by 

 contraction of the smaller arteries, from irritation of the vasomotor centre. 

 The heart is enfeebled by a want of oxygen and inhibited in its action by 

 the inhibitory centres. 



ANIMAL HEAT. 



The Functional Activity of all the organs and tissues of the body is 

 attended by the evolution of heat, which is independent, for the most part, 

 of external conditions. Heat is a necessary condition for the due perform- 

 ance of all vital actions ; though the body constantly loses heat by radia- 

 tion and evaporation, it possesses the capability of renewing it and main- 

 taining it at a fixed standard. The normal temperature of the body in the 

 adult, as shown by means of a delicate thermometer placed in the axilla, 

 ranges from 97.25 Fahr. to 99.5 Fahr., though the mean normalizm.- 

 perature is estimated by Wunderlich at 98.6 Fahr. 



The temperature varies in different portions of the body, according to 

 the degree in which oxidation takes place ; being the highest in the muscles 

 during exercise, in the brain, blood, liver, etc. 



The conditions which produce variations in the normal temperature 

 of the body are : age, period of the day, exercise, food and drink, climate, 

 season and disease. 



Age. At birth the temperature of the infant is about i F. above that of 

 the adult, but in a few hours falls to 95.5 F., to be followed in the course 

 of 24 hours by a rise to the normal or a degree beyond. During childhood 

 the temperature approaches that of the adult; in aged persons the tempera- 

 ture remains about the same, though they are not as capable of resisting 

 the depressing effects of external cold as adults. A dittrnal variation of 

 the temperature occurs from 1.8 F. to 3.6 F. (Jurgensen) ; the maximum 

 occurring late in the afternoon, from 4 to 9 P. M., the minimum, early in 

 the morning, from I to 7 A. M. 



Exercise. The temperature is raised from i to 2 F. during active 

 contractions of the muscular masses, and is probably due to the increased 

 activity of chemical changes ; a rise beyond this point being prevented by 

 its diffusion to the surface, consequent on a more rapid circulation, radia- 

 tion, more rapid breathing, etc. 



