INFECTIONS OF THE DIGESTIVE TRACT 307 



less robust and less capable of rapid recuperation under 

 favorable hygienic conditions. After a time com- 

 monly, however, not until the process has been a very 

 marked one for ten or fifteen years the patients lose 

 so much strength as to be unable to attend to ordi- 

 nary business occupations without very great effort. A 

 period of carefully regulated living, free from anxieties, 

 may be followed by a considerable degree of improve- 

 ment, but this improvement is usually extremely slow. 

 In certain cases the anaemia ultimately deepens, and the 

 patient may present the picture of a progressive per- 

 nicious anaemia. In other instances it is especially 

 the nervous symptoms which increase, and periods of 

 depression become more and more marked and of longer 

 duration. The mental depression may become so pro- 

 nounced as to necessitate a residence of the patient in 

 a sanitarium or asylum, the conditions being those of 

 mild or pronounced melancholia. As already mentioned 

 when discussing the character of the toxic effects of the 

 various poisons absorbed from the intestine, it is highly 

 probable that different individuals react differently to 

 the same toxic agencies. If, for example, there be 

 absorbed from the intestine substances capable of 

 damaging both the nervous system and the red blood 

 cells, it is conceivable (assuming the same proportions 

 and amounts of these substances to be absorbed in each 

 instance) that one individual would become invalided 

 first through damage to the nervous system, whereas 

 the invalidism of another might come first through dam- 

 age to the blood. The condition of invalidism in either 



