678 ANIMAL HEAT 



creased, while the urea is relatively decreased, even when its abso- 

 lute amount is greater than normal. Kreatin, which is not normally 

 present in urine, unless the food contains it, may also appear in 

 fever (Shaffer). It has been suggested that the proximate cause of 

 fever is the action of bacterial poisons or of other substances on the 

 ' heat centres,' and that antipyretics, or drugs which reduce the 

 temperature in fever, do so by restoring the centres to their normal 

 state, by preventing the development of the poisons, aiding their 

 elimination, or antagonizing their action. In favour of this view, 

 it has been stated that when the basal ganglia are cut off, by section 

 of the pons, from their lower nervous connections, fever is no longer 

 produced by injection of cultures of bacteria which readily cause it 

 in an intact animal, while antipyrin has no influence upon 

 the temperature (Sawadowski). And while it is almost certain 

 that some pyrogenic or fever- producing agents cocaine, e.g. act 

 indirectly, 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 imme- 

 diately upon the heat-forming tissues, so as to diminish their 

 metabolism, while others, like antipyrin, affect them through the 

 nervous system. Quinine has no influence upon ' puncture ' fever 

 in rabbits. A still more important 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 bloodvessels 

 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 consider a little more closely the possible ways in which a 

 rise of temperature 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 (Fig. 215) 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 infrequently dimin- 

 ished loss and increased production may be both involved; and it 

 ought to be remembered that the healthy standard with which the 

 heat-production of a fever patient should be compared is not that 

 of a man doing hard work on a full diet, but that of a healthy person 

 in bed, and on the meagre fare of the sick-room. When this is kept 

 in view, the comparatively low heat-production and respiratory 

 exchange which have sometimes been found in fever cease to excite 



