ANIMAL HEAT. 451) 



of carbon dioxide given out are both increased, and with this there must 

 be increased metabolism of the tissues, and particularly of the muscular 

 tissues, since at the same time the amount of urea in the urine is 

 increased. Every one is familiar with the rapid wasting which is such 

 a characteristic of high fever; it must indicate not only too rapid 

 metabolism of the body, but also insufficient time for the tissues to build 

 themselves up. In fever then there may be supposed to be some inter- 

 ference in the ordinary channel by which the skin is able to communi- 

 cate to the nervous system the necessity of an increased or diminished 

 production of heat in the muscles and other tissues. In consequence of 

 this, and in spite of the condition of heat of the surface of the body, 

 the production of heat goes on at an abnormal rate. It is not certain 

 in what way the centre acts, whether it is one which keeps the meta- 

 bolism in check, and when out of gear it is no longer able to do this, or 

 whether, on the other hand, it is a centre by means of which the meta- 

 bolism of the tissues may be increased by stimuli proceeding from it. 

 Impulses from the skin would, according to these two possible modes 

 of action, act either in the direction of increasing its inhibitory action, 

 or in the direction of increasing or of diminishing the different stimuli 

 causing increased production. 



Influence of Extreme Heat and Cold. In connection with the 

 regulation of animal temperature, and its maintenance in health at the 

 normal height, may be noted the result of circumstances too powerful, 

 either in raising or lowering the heat of the body, to be controlled by the 

 proper regulating apparatus. Walther found that rabbits and dogs kept 

 exposed to a hot sun, reached a temperature of 46 C. (114.8 F.), and 

 then died. Cases of sunstroke furnish us with several examples in 

 the case of man ; for it would seem that here death ensues chiefly or 

 solely from elevation of the temperature. 



The effect of mere loss of bodily temperature in man is less well known 

 than the effect of heat. 'From experiments by Walther, it appears that 

 rabbits can be cooled down to 8.9 C. (48 F.), before they die, if arti- 

 ficial respiration be kept up. Cooled down to 17.8 C. (64 F.), they 

 cannot recover unless external warmth be applied together with the 

 employment of artifical respiration. Babbits not cooled below 25 C. 

 (77 F.) recover by external warmth alone. 



