270 FUNCTIONS OF NUTRITION. 



temperature, if he be supplied with artificial warmth up to a certain 

 point, he may regain his vitality, and the processes of life be again put 

 in operation. The respiration, which had been reduced to a minimum 

 by the action of cold, gains in rapidity as the body is artificially 

 warmed, and the functions of the nervous and muscular systems are 

 finally restored. 



A striking example of temporary suspension of the bodily functions 

 by cold is presented by the hibernating animals, which pass into a con- 

 dition of torpor during the winter, becoming insensible, unconscious, 

 and motionless, while respiration is nearly imperceptible, and the bodily 

 temperature sinks to 10, or even below it Life, however, is not abol- 

 ished, but only held in abeyance ; and with the return of spring all the 

 functions resume their activity. A hibernating animal is somewhat in 

 the condition of a seed, which remains in the ground over winter, with 

 its vitality dormant, and ready to come into action when supplied with 

 the requisite warmth. 



Effects of Elevating the Temperature of the Animal Body. If the 

 temperature of the body be raised above the normal standard, the 

 effects are quite different from those produced by cold. In the obser- 

 vations of Bernard, on birds and mammalians confined in heated air, 

 with due ventilation, the primary effects were increased frequency of 

 respiration with discomfort and agitation ; and death was usually 

 accompanied with convulsive movements, or preceded by an audible 

 cry. The fatal result was more rapidly produced in birds than in 

 mammalia. A rabbit, in air at 65, died in twenty minutes ; and a 

 bird, in air at the same temperature, in four minutes. This difference 

 is probably due to the greater activity of the circulation in birds, by 

 which external heat is more rapidly transferred to the internal organs ; 

 since the same observer found that when two rabbits, one living and 

 one dead, were placed in air at 100, the internal temperature of the 

 living animal became sensibly raised sooner than that of the dead one. 

 In a medium of high temperature, therefore, a fatal amount of heat 

 reaches the internal organs more rapidly by the circulation than by 

 conduction through the solid tissues. 



After death from exposure to too warm an atmosphere, the internal 

 temperature is found to be 5 or 6 above the normal standard; the 

 heart is motionless ; both the muscles and the nerves are insensible to 

 galvanism ; and cadaveric rigidity is established with unusual prompt- 

 itude. In many instances the blood is found dark-colored in the arte- 

 rial as well as in the venous system ; but this is a post-mortem 

 change, since observation shows that the arterial blood continues red 

 during life, while its oxygen disappears and its color darkens after 

 the stoppage of respiration. A high temperature produces death appa- 

 rently by hastening, in undue measure, the chemical changes in the 

 tissues and fluids, so that their vitality is rapidly exhausted and can 

 no longer be maintained by the usual processes of nutrition. 



Resistance of the Body to Low External Temperatures. Since an 



