160 RELATIONS OF BACTERIA TO DISEASE 



where the bacilli are selective in their field of operation, as in 

 croupous pneumonia or typhoid, sometimes being of a very ir- 

 regular kind, especially when the bacteria from time to time 

 invade fresh areas of the body, as in pysemic affections. The 

 main point of interest regarding the development of fever is as 

 to whether it is a direct effect of the circulation of bacterial 

 toxins, or if it is to be looked on as part of the reaction of the 

 body against the irritant. This question has still to be settled, 

 and all that we can do is to adduce certain facts bearing on it. 

 Thus in diphtheria and tetanus, where toxic action leading to 

 degeneration plays such an important part, fever may be a very 

 subsidiary feature, except in the terminal stage of the latter 

 disease ; and in fact in diphtheria profoundly toxic effects may 

 be produced with little or no interference with heat regulation. 

 On the other hand, in bacterial disease, where defensive and re- 

 parative processes predominate, fever is rarely absent, and it is 

 nearly always present when an active leucocytosis is going on. 

 In this connection it may be remarked that several observers 

 have found that, when a relatively small amount of the dead 

 bodies of certain bacteria are injected into an animal, fever 

 occurs ; while the injection of a large amount of the same is 

 followed by subnormal temperatures and rapidly fatal collapse. 

 It might appear as if this indicated that the occurrence of fever 

 had a beneficial effect, but this is one of the points at issue. 

 Certainly such an effect is not due to the bacteria being unable 

 to multiply at the higher degrees of temperature occurring in 

 fever, for this has been shown not to be the case. Whether the 

 increase of bodily temperature indicates the occurrence of 

 changes resulting in the production of bactericidal bodies, etc., 

 is very doubtful ; a production of antagonistic substances may 

 be effected without the occurrence of fever or of any appar- 

 ent disturbance of health. If we consider the site of the heat 

 production in fever we again are in difficulties. It might appear 

 as if the tissue destruction, indicated by the occurrence of fatty 

 degeneration, would lead to heat development, but frequently 

 excessive heat production with increased proteid metabolism 

 occurs without any discoverable changes in the tissues; and 

 further, in phosphorus poisoning there is little fever with great 

 tissue destruction. The increased work performed by the heart 

 in most bacterial infections no doubt contributes to the rise of 

 bodily temperature. But we must bear in mind that in fever 

 there is more than mere increase of heat production there is 

 also a diminished loss of heat from interference with the nervous 

 mechanism of the sweat apparatus. The known facts would 



