752 METABOLISM 



tration of chlorides in the blood is considerably increased, whereas in fever 

 it is markedly diminished. The deficiency in salt elimination cannot be at- 

 tributed to a deficiency of salt in the food, for it sets in before the diet 

 has been curtailed and, when salt is given to a febrile patient, it is re- 

 tained in the body to a greater degree than is the case in the normal 

 individual. 



Belonging to this group of fevers must also be considered the im- 

 portant ones produced by the intravenous injection of certain forms of 

 protein, as those of egg white or those derived from the bodies of bac- 

 teria or from the laked corpuscles of a foreign blood. The fever in 

 these cases is no doubt caused by a mechanism closely related to that 

 responsible for anaphylaxis (see page 90). It is believed that many cases 

 of so-called aseptic fever, occurring after severe contusions or other 

 wounds, may be the result of destruction of proteins within the body. 

 Similarly the rise in temperature during infections may be owing to 

 the breakdown of protein by microorganisms within the cells. 



The Essential Cause of Fever 



It is possible that the essential cause for fever is that poisonous sub- 

 stances (such as toxins) cause the tissues to break down and so increase 

 the osmotic pressure of their protoplasm. Water is therefore attracted 

 into them from the blood, the volume of which in circulation is thereby 

 reduced. This reduction affects the superficial capillaries relatively more 

 than the deeper ones and so tends to cool down the skin, as a result 

 of which the nervous reflexes against cold are aroused and the superficial 

 capillaries constricted. The view that removal of water from the blood 

 is a most important element in fever is supported not only by the fact, 

 already stated, that the blood has been found to be more concentrated 

 in fever but also by numerous observations on the influence of drugs. 

 Those which cause concentration of blood are likely also to cause rise 

 in body temperature, such, for example, as certain diuretics (purines, 

 sugars, etc.), intravenous injection of hypertonic salt solutions (3 per 

 cent Nad) and certain cathartics, such as aloin. Cocaine causes fever 

 partly by blood concentration. Antipyretics, on the other hand, (such as 

 acetyl salicylic acid) act mainly by increasing heat elimination, although 

 under certain conditions (as in coli fever) they may also cause dilution of 

 the blood (Barbour). 



While increased concentration of the blood is undoubtedly an impor- 

 tant factor in fever it must also be remembered that upset of the control 

 of heat production and loss through action on the heat regulating or 

 thermogenic centers may also be involved. 



