Fever. 167 



terminate fatally {heat stroke). The occurrence of a heat stroke 

 is marked by symptoms of general weakness, dizziness, fainting 

 attacks, and marked acceleration of the pulse, these probably being 

 mainly dependent upon disturbances of brain and myocardium, al- 

 though upon this point there is need of further study. 



Fever {fehris, from fervere, to be hot) is a state of the body 

 in which because of some disturbance of metabolism the regulation 

 of the body temperature to a mean level has ceased. The chief 

 and most constant evidence of fever is the abnormal increase of 

 the temperature of the blood, or internal body temperature. This 

 febrile hyperthermia or fever heat may exceed the normal tem- 

 perature of the animal perhaps but half a degree or by from 

 two to five degrees centigrade. It is characterized by marked re- 

 sistance to influences causing heat dissipation and by considerable 

 variation ; and is accompanied by increased tissue waste, changes 

 in the type of and increased frequency of the arterial pulse, increase 

 in the rate of respiration, diminution and alterations in the various 

 secretions, particularly in the urine, disturbances in the sensory 

 apparatus, increased thirst and loss of appetite. This group of 

 symptoms, which occur with the heightened temperature and with 

 it go to make up the clinical picture of fever, are to a slight 

 extent directly dependent upon the increased temperature of the 

 blood (for example, the number of cardiac movements and respira- 

 tions), but for the greater part are the results of the complex 

 action of the causes of the fever. The main point in the conception 

 of fever, with its febrile excess of temperature, is that the latter 

 is not the mere result of external physical influences restricting 

 thermolysis, or of muscular activity, but that there are certain 

 metabolic processes in operation which are due to the presence of 

 special temperature producing substances {pyrogenetic substances) 

 which give origin to the hyperthermia. How the heat equilib- 

 rium is aft'ected by such substances, whether they directly dis- 

 engage the heat from the cells and cellular groups or whether 

 they act indirectly through a heat centre, is not as yet certain and 

 cannot even in a general way be explained. These pyrogenetic 

 substances vary much among themselves and the reaction? which 

 they give rise to are by no means uniform. P""ever may be thovight 

 of as an indicator (Wassermann) that some peculiar metabolic 

 processes are in operation in the body accompanied by tissue 

 destruction and the production of antitoxic and bactericidal sub- 

 stances and precipitins ; and may be considered as an associated 



