450 STORAGE OF HEAT IN THE BODY. 



Rabbits placed in a warm box at 36 Q C. acquire a constant temperature of 42C., 

 and lose weight; but if the temperature of the box be raised to 40, death occurs, 

 the body-temperature rising to 45C. (J. Rosenthal). 



219. Storage of Heat in the Body. 



As the uniform temperature of the body, under normal circumstances, 

 is due to the reciprocal relation between the amount of heat produced 

 and the amount given off, it is clear that heat must be stored up in the 

 body when the evolution of heat is diminished. The skin is the chief 

 organ regulating the evolution of heat; when it and its blood-vessels 

 contract, the heat evolved is diminished, when they dilate it is increased. 

 Heat may be stored up when 



(a) The skin is extensively stimulated, whereby the cutaneous vessels are tem- 

 porarily contracted (Rb'hrig). (b) Any other circumstances prevent heat from 

 being given off by the skin (Winternitz). (c) When the vaso-motor centre is 

 excited, causing all the blood-vessels of the body those of the skin included to 

 contract. This seems to be the cause of the rise of temperature after transfusion 

 of blood (Landois), and the rise of temperature after the sudden removal of water 

 from the body seems to admit of a similar explanation ; as the inspissated blood 

 occupies less space, and the contracted vessels of the skin admit less blood. 

 (d) When the circulation in the cutaneous vessels of a large area is mechanically 

 slowed, or when the smaller vessels are plugged by the injection of some sticky 

 substance, or by the transfusion of foreign blood, the temperature rises ( 102). 

 Landois found that ligature of both carotids, and the axillary and crural arteries, 

 caused a rise of 1C. within two hours. 



It is also obvious that when a normal amount of heat is given off, an 

 increased production of heat must raise the temperature. The rise of the 

 temperature after muscular or mental exertion, and during digestion 

 seems to be caused in this way. The rise which occurs several hours 

 after a cold bath is probably due to the reflex excitement of the skin 

 causing an increased production (Jiirgensen). 



When the temperature of the body, as a whole, is raised 6C., death 

 takes place, as in sunstroke. It seems as if there was a molecular de- 

 composition of the tissues at this temperature; while, if a slightly 

 lower temperature be kept up continuously, fatty degeneration of many 

 tissues occurs (Litten). If animals, which have been exposed artifici- 

 ally to a temperature of over 42-44C., be transferred to a cooler 

 atmosphere, their temperature becomes sub-normal (36C.) and may 

 remain so for several days. 



220. Fever. 



Fever consists in a greatly increased tissue metabolism (especially in the muscles 

 Finkler, Zuntz), with simultaneous increase of the temperature. Of course the 

 mechanism regulating the balance of formation and expenditure of heat is disturbed. 



