150 HUMAN PHYSIOLOGY. 



The heterogeneous composition of venous blood is exchanged for 

 the uniform composition of the arterial. 

 It gains oxygen and loses carbonic acid. 

 Its coagulability is increased. Temperature is diminished. 



Asphyxia. If the supply of oxygen to the lungs be diminished 

 and the carbonic acid retained in the blood, the normal respiratory 

 movements cease and the condition of asphyxia ensues, which soon 

 terminates in death. 



The phenomena of asphyxia are violent spasmodic action of the 

 respiratory muscles attended by convulsions of the muscles of the 

 extremities, engorgement of the venous system, lividity of the 

 skin, abolition of sensibility and reflex action, and death. 



The cause of death is a paralysis of the heart from overdistention 

 by blood. The passage of the blood through the capillaries is pre- 

 vented by contraction of the smaller arteries, from irritation of the 

 vasomotor center. The heart is enfeebled by a want of oxygen and 

 inhibited in its action by the inhibitory centers. 



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 performance of all vital actions ; although the body con- 

 stantly loses heat by radiation and evaporation, it possesses the 

 capability of renewing it and of maintaining 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 

 F. to 99.5 F., though the mean normal temperature is estimated by 

 Wunderlich at 98.6 F. 



The temperature varies in different portions of the body accord- 

 ing to the extent to which oxidation takes place, being highest in the 

 muscles, in the brain, blood, liver, etc. 



The conditions which produce variations in the normal tempera- 

 ture 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 



