DISTURBANCES OP METABOLISM, ETC. 185 



in metabolism the most difficult to understand is the occurrence 

 of that interference with the heat-regulating mechanism which 

 results in fever. The degree and course of the latter vary, 

 sometimes conforming to a more or less definite type, where the 

 bacilli are selective in their field of operation, as in croupous 

 pneumonia or typhoid, sometimes being of a very irregular 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 dp is to adduce certain facts bearing on it. Thus in diph- 

 theria 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 reparative 

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

 always present when there is an active leucocytosis 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 apparent 

 disturbance of health. 



Symptoms. — Many of the symptoms occurring in bacterial 

 infections are produced by the histological changes mentioned, 

 as can be readily understood ; whilst in the case of others, corre- 

 sponding changes have not yet been discovered. Of the latter, 

 those associated with fever, with its disturbances of metabolism 

 and manifold affections of - the various systems, are the most 

 important. The nervous system is especially liable to be 

 affected — convulsions, spasms, coma, paralysis etc., being 



