492 GENERAL CONSIDERATIONS 



injected protects the body from the effect of such agents. Autogenous 

 vaccines may be prepared from a person suffering from an infection and 

 given to him to combat the infection. 



551. Anaphylaxis and Allergy. — Anaphylaxis may be defined as an 

 exaggerated irritabihty of the body with respect to some foreign sub- 

 stance. It may follow a case of mild poisoning by the substance con- 

 cerned and is associated with the eating of a great many foods, 

 particularly proteins and sea foods. A person may have eaten such a 

 food freely and without evil effects until, under certain conditions, poison- 

 ing occurs. If thereafter, whenever the food is taken, the body shows a 

 pronounced reaction, a case of anaphylaxis exists. Allergy is a similar 

 exaggerated susceptibility to contact with dust, the pollen of plants, and 

 hairs or other particles from the bodies of animals. Hay fever is such a 

 condition. The word allergy is sometimes used in a more general sense 

 to include anaphylaxis and immunity, thus referring to any altered 

 response of the body to foreign substances of any kind. 



552. Maintenance of Health in Human Beings. — Many of the condi- 

 tions which are necessary to maintain the body in a state of health may be 

 inferred from statements made earlier in this chapter. The field of 

 investigation which deals with the effect of conditions within the body 

 upon health is called hygiene; when conditions outside the body are 

 involved, it is spoken of as sanitation. Preventive medicine covers in 

 general both fields. 



Always in considering the maintenance of health allowances must 

 be made for the effect of routine. The body forms habits relating to 

 all procedures connected with hygiene and these have the same control 

 over the body, when once formed, as do all habits. In changing in any 

 way his mode of living a person has to consider the adjustment which the 

 body can make. This power of adjustment is great in youth but dimin- 

 ishes rapidly in old age, when changes of any kind have to be gradually 

 brought about. 



