A MANUAL OF PHYSIOLOGY 



directly, through the brain or cord, it is quite possible that 

 others affect directly the activity of the tissues in general, 

 just as some antipyretics or fever-reducing agents, such as 

 quinine, act immediately upon the heat-forming tissues, so 

 as to diminish their metabolism, while others, like antipyrin, 

 affect them through the nervous system. A still more im- 

 portant action of antipyrin, and the group of antipyretics to 

 which it belongs, is the increase in the heat-loss which they 

 bring about by the dilatation of the blood-vessels of the skin. 

 This effect is also produced through the nervous system. 

 Fever is a condition so interesting from a physiological 



point of view, and of 

 such importance in 

 practical medicine, that 

 it will be well to con- 

 sider a little more 

 closely the possibleways 

 in which a rise of tem- 

 perature may occur. It 

 must not be forgotten 

 that the febrile increase 

 of temperature is always 

 accompanied by other 

 departures from the 

 normal, and that all 

 the fundamental febrile 

 changes may even, in 

 certain cases, be present 

 without elevation, and 

 even with diminution of 

 temperature. But here 

 we have only to do with 

 the disturbance of the 

 normal equilibrium between the loss and the production 

 of heat ; and it is evident that any of the five conditions 

 illustrated in the diagram may give rise to an increase 

 of temperature. It is not necessary to discuss whether 

 cases of fever can actually be found to illustrate every 

 one of these possibilities. It is probable that not infre- 



FIG. 142. DIAGRAM TO SHOW THE POSSIBLE 

 RELATIONS BETWEEN HEAT-PRODUCTION 

 AND HEAT-LOSS IN FEVER. 



