FEl'ER. 525 



comparatively insignificant does not require to be discussed 

 here. 



Pyrexia. The temperature of the body may be abnormally 

 raised in several ways. Thus we meet with excessive pyrexia 

 in injury or disease of the heat-centre or tracts, especially 

 injury of the cervical and dorsal regions of the spinal cord. 

 Exposure to excessive heat induces " heat-fever," a variety of 

 sunstroke which is common in India. More familiar to us is 

 fever brought on by interference with the refrigerating function 

 of the skin, as the effect of exposure to cold or damp. This is 

 known as a " chill." A powerful impression of cold on the 

 afferent nerves of temperature appears to throw the regulating 

 mechanism into disorder; perspiration is arrested; the cuta- 

 neous vessels are spasmodically contracted; rigors, shivers, or 

 chilly feelings ensue ; and the heat thus retained in the blood 

 quickly raises the temperature. 



Increased production of heat at one focus, such as an in- 

 flamed part, contributes in an insignificant degree to the accom- 

 panying fever. 



The increased production of heat in the tissues generally 

 which is probably present in all kinds of fever, whatever its 

 cause, is no doubt the principal origin of the pyrexia. The in- 

 creased activity of metabolism is proved by the rapid wasting 

 of the tissues, by the increase of urea and other excretions, and 

 by the pyrexia as tested by the thermometer all obvious phe- 

 nomena in every case attended by fever. 



In the specific fevers there is at work, however, another 

 cause of oxydation of the tissues, which f urnishes an extraneous 

 addition to the body heat. We now believe that many diseases, 

 such as typhoid fever, small-pox, and septicaemia, are associated 

 with the presence of organisms in the tissues, if not actually 

 caused by them. The life of such organisms, the processes of 

 fermentation with which they are associated, and the destruc- 

 tion of the tissues which they produce, must all be a consider- 

 able source of heat within the body, in a way perfectly foreign 

 to the normal processes, though closely resembling some of 

 them. 



A combination of several of the preceding causes is commonly 

 at work in fever. Thus, when a patient has a local wound 

 which acts as a focus of heat, the pus may decompose, i.e. be- 

 come infected by organisms ; these are absorbed into and 

 flourish in the blood ; fresh foci of disease are set up in the 

 tissues ; and the natural refrigeration of the blood is reduced by 

 the disturbances of the skin, lungs, and circulation, which 

 always accompany serious illness. 



Perspiration. Only two disorders of perspira- 



