180 DISEASES DIE TO MALADJUSTMENT 



There are certain remote effects of injury, however, which 

 are properly called disease because they involve failure in 

 the internal adjustments of the cells. These will be con- 

 sidered briefly in a subsequent paragraph. 



Finally, there are the numerous and serious malad- 

 justments which arise from the struggle for existence 

 among competing organisms and which are familiar in the 

 so-called infectious diseases. For convenience in pre- 

 sentation, the diseases which fall under this latter head, 

 instead of being included here, will be considered sepa- 

 rately in the section on " Associations of Organisms " 

 (Chap. XX). 



Nature of Disease. — Metabolism is made up of three 

 different stages, (1) the taking up of materials by the 

 cells, (2) the utilization of these materials in the chem- 

 ical processes which go on within the cells, and (3) the 

 discharge of the waste products which result from the 

 chemical processes. Disease is a disturbance, either in the 

 amount of metabolism, in which case the quantities of 

 material consumed, the volume of the chemical activity, 

 and the amount of waste products poured out may be 

 increased or diminished; or it may be a change in the 

 character of the metabolism, in which case the substances 

 utilized by the cells will be different, the character of the 

 chemical processes will be changed, and the waste prod- 

 ucts poured out will be of different sorts. It is true, of 

 course, that in many diseases — and perhaps in most — 

 both the amount and character of the metabolism are 

 altered. 



Symptoms of Disease. — By definition, a symptom of 

 disease is a bodily manifestation resulting from the dis- 

 turbed metabolism which constitutes the disease itself. 

 A healthy body, functioning normally, has certain repre- 

 sentative appearances which are recognized as attributes 

 of health. In man. for example, there is a certain range 

 of rapiflity of heart-beat which is characteristic of good 

 health. When the heart rate is outside this range, either 



