138 PHYSIOLOGY FOR DENTAL STUDENTS. 



morning in such a patient, a slight degree of fever might quite 

 easily be missed, because at this time the normal temperature is 

 low. In acute infectious diseases, the afternoon temperature 

 may rise to 106 F. or 41 C., or even above this, without prov- 

 ing fatal. A temperature of 113 F. or 45 C. has been observed, 

 but lasting for only a short time. Fever is always higher in in- 

 fants and young children than in adults. 



As to the causes of fever, two possibilities exist : either ( 1 ) that 

 heat production has been increased, or (2) that heat loss has 

 been diminished, or, of course, both factors may operate simul- 

 taneously. To go into this unsolved problem is unnecessary here ; 

 suffice it to say that there can be no doubt that disturbance in 

 the thermogenic centre is the underlying cause of fever, and 

 that it is the avenues of heat loss by the skin rather than the 

 sources of heat supply in the muscles that are first of all acted 

 on. The cold sensation down the back, the shivering, the goose 

 skin, are the familiar initial symptoms of fever, and when the 

 fever comes to an end, excessive sweating sets in and this, in part 

 at least, explains the fall in temperature. Increased combustion 

 in the muscles no doubt occurs during the height of the fever 

 and accounts for the great wasting, but that this is not the only 

 cause of the rise in temperature is evidenced by the fact that 

 severe muscular exercise does not in itself cause fever, even 

 although there may be much more combustion going on in the 

 body (see p. 88). 



Certain drugs called antipyretics lower the temperature in 

 fever. The most important of these are acetanilide, salicylates 

 (aspirin), phenacetin, and quinine. The first three mentioned 

 act on the thermogenic centre, whereas quinine seems to act 

 directly on the combustion processes in the muscles. The body 

 temperature is raised by cocaine and by the toxic products of 

 bacterial growth. Even cultures which have been attenuated by 

 keeping them for some time at high temperatures have this 

 effect, and it is believed by many that fever is of the nature of 

 a protective mechanism to destroy or attenuate the invading 

 bacteria. There is bacteriological as well as clinical support for 

 this view, thus, certain pathogenic organisms (such as the strep- 



