DISEASE 285 



destruction of its tissue and the poison of the toxin. As 

 a result, it quickly succumbs to the disease. 



Four stages of disease. The ordinary course of any 

 disease is dependent upon the conditions of the inva- 

 sion and the resistance of the body to it. It has 

 four distinct stages. First there is a period of incu- 

 bation, during which the microbes are gaining strength 

 by multiplying in numbers. This period begins at the 

 time of exposure, that is, at the time of the first entrance 

 of the microbes into the body, and ends at the first symp- 

 toms of disease, as nausea, headache and fever. The 

 second stage is a period of development of the disease, 

 due to continued activity and multiplication of the 

 microbes. During this period, the resistance of the body 

 is beginning. During the third period, the fight be- 

 tween the microbes and the body is raging. If the 

 body is able to make a good resistance, the disease ceases 

 to increase and maintains a level. At the end of this 

 period, which may be short or long as determined by 

 the nature of the disease and the body's power of re- 

 sistance, the fourth period commences. The disease 

 either begins to abate, if the body has been successful 

 in its manufacture of antibody; or to increase, if it has 

 been unsuccessful. The decline of the disease may be 

 sudden, as in the crisis of pneumonia, in which case the 

 microbes seem to be speedily and completely over- 

 whelmed; or the decline may be slow, as is much more 

 usual. 



Individual differences in resistance. The power of 

 the body to develop antibodies to meet disease varies 

 greatly in different individuals. -This difference is shown 

 especially in the attitude of the white blood corpus- 

 cles toward the invading microbes. In some persons, 

 they seem to be indifferent to them ; in others, they seize 



