94 INFECTIOUS AND PARASITIC DISEASES. 



action of poisons, or in which the tension of the work 

 is a §evere strain upon the nervous system. Some 

 poisons per se produce pathological states, e.g., lead, 

 arsenic, mercury, etc. These also tend to the produc- 

 tion of an impoverished state of the blood (anaemia), 

 constipation, etc., abnormalities which we already 

 have called attention to as paving the way for infections. 

 Occupations involving severe strains disturb the nervous 

 system, which in turn affects the nutrition and func- 

 tions of every part of the body. 



In Ogle's table illustrating the comparative mortality 

 in the various occupations, innkeepers and liquor 

 dealors are seen to head the list in point of frequency. 

 This is not because there is anything especially injurious 

 in the occupation, but because the occupation usually 

 leads to excessive indulgence in intoxicants. So well 

 recognized is this association of alcoholism with the 

 handling or sale of liquors, that life insurance com- 

 panies universally regard individuals of this class as 

 bad ^^ risks" and refuse to insure their lives. 



The incidence of age and disease is well 

 Age. established. There are disorders of in- 

 fancy, of childhood, of adolescence, and 

 of old age. Middle life also has its afflictions in the 

 way of special diseases, but as we are limited to in- 

 fectious diseases, and they are not associated to any 

 marked extent with this period, the affections peculiar 

 to it will not be discussed. 



