THE CAUSATION OF DISEASE. 265 



Note that I say fated diseases, for it is manifest that the 

 minor inheritable diseases, which do not cause death, cannot 

 fall under the influence of natural selection ; and that I make 

 the further qualification, elite to inherited structured peculiarity — 

 that is to say, not to peculiarities of E. 



Now, there are several circumstances which render it difficult 

 to test the truth of the above statement. In the first place, it 

 is necessary to remember that many diseases begin early in 

 life, yet do not kill till the individual is far advanced in pro- 

 creative life or has actually passed it. A good example is 

 afforded by rheumatic diathesis. I suppose the majority of 

 people who suffer from rheumatism outlive procreative life ; 

 certainly many live on far into it. It is true that this disorder 

 must diminish the chances of matrimony, but it is questionable 

 whether it does so in a marked degree. It therefore follows 

 that many rheumatically-disposed individuals may rear children, 

 even though they have suffered from the disease in early life. 



Then, again, it might be thought that the rate of the mor- 

 tality at different periods of life would give us the proportion 

 of inherited structural peculiarities at these several periods, but 

 this is by no means the case, and for these reasons : First, 

 the "disease-tendency at the several periods of life is not the 

 same thing as the amount of disease, because much depends 

 upon the nature of the E, and this is more pathogenic during 

 certain periods than others. Every one knows, for instance, 

 that in men the mortality is largely increased by the nature of 

 their occupation, by overwork, worry, accident, and so forth ; 

 that in women there are many disorders connected with their 

 peculiar mental and physical surroundings ; and that infants 

 and young children, notably those of the lower classes, are 

 (owing to defect in "reason" on the part of the parents) 

 subjected to peculiar unhealthy conditions, such as improper 

 feeding and clothing. Secondly, the disease-tendency ' at 

 any particular period of life may not be due to any 

 special inherited weakness, but to a condition of body more 

 or less common to all members of one or both sexes at that 

 period. Thus during the procreative period all women are 

 subject to dangers from which they are free before and after 

 this period. Children, too, are especially prone to respond 



