DEFENSES OF THE BODY 135 



excess, and this leads to a wholly different set of 

 manifestations. Here, then, disease is caused either 

 by a deficiency or excess of a normal secretion by 

 the agency of disproportion. Another striking ex- 

 ample of the same phenomena is seen in the way in 

 which ulcer of the stomach arises. The mucous 

 membrane of the stomach secretes a juice capable of 

 digesting meat fibers, yet it is a remarkable thing 

 that this juice fails to digest the stomach itself. 

 The living cells of the stomach are able to resist 

 chemical conditions which the dead or dying cells 

 cannot withstand. The power of resistance which 

 these cells exhibit seems to depend on their possess- 

 ing special ferments capable of defying the powerful 

 digestive ferments of the gastric juice. Under 

 certain pathological conditions, the resistant fer- 

 ments are probably lost in a portion of the mucous 

 membrane of the stomach which consequently be- 

 comes helpless to the attack of the gastric juice, and 

 the formation of ulcer results. In many cases, the 

 lack of balance in physiological powers is less plain, 

 but still probable. So in cancer the invading cells 

 run riot, probably because the habitual restraining 

 forces of these cells have been in some way lost. 



In general, it seems correct to regard the pro- 

 cesses of disease as differing from those of health in 

 a quantitative, rather than a qualitative, way. A 

 living cell, like a liver cell, may be considered as a 

 field within which there is a largely independent 

 play of distinct processes each process being 



