308 CHARLES HERRMAN 



prevention of contact infection, the earlier diagnosis and more efficient 

 treatment, but in addition to a certain extent the susceptible strains have 

 been eliminated. It will be noted (chart 9) that in the first ten years of this 

 century there was a marked reduction in the mortality from tuberculosis 

 in infants as compared to the total mortality from this disease. There 

 may be a distinct difference in the mortality from tuberculosis in different 

 groups living in the same city under similar environmental conditions. 

 Fishberg (7) reported that in New York City from 1885 to 1890, the death 

 rates from tuberculosis were, taking the Poles and Russians (principally 

 Jews) as 100: 



Hungarians 158 



Americans 209 



English 329 



Germans 335 



Irish 659 



Negroes 759 



Chart 10 shows the mortality from tuberculosis among the Jews in 1925, 

 as compared to the general population, and also the registration area of the 

 United States. Environmental conditions are similar, in fact a large num- 

 ber of Jews are poor and live in the lower east-side of the Borough of Man- 

 hattan, in crowded and not too sanitary tenements, where the opportunity 

 for contact infection is very great. Notwithstanding, the mortality at all 

 ages is distinctly less. The accepted explanation is that having lived in 

 Ghettos for centuries, a selective process has eliminated the most susceptible 

 strains. This is well illustrated by the following observation reported by 

 Boyd (8). "The war has recently furnished an interesting example of the 

 truth that when members of an isolated community in which tuberculosis is 

 rare are brought into contact with people among whom tuberculosis is 

 common, they show extreme susceptibility to the disease. The example is 

 provided by the inhabitants of Jerusalem. Two classes of Jews have re- 

 turned from their exile of centuries. The first comprises the Jews scattered 

 all over Europe and America, living in the most crowded districts of the 

 great cities under the worst conceivable conditions, but with an acquired 

 immunity so great that the disease has no terrors for them. There is uni- 

 versal tuberculous infection but no tuberculous disease. The tuberculin 

 test is positive. The second group is that of the Jews of the Yemen, who 

 have led an isolated nomadic life in the Arabian desert and for centuries 

 have been shielded from tuberculous infection. The tuberculin test is 

 negative. These two groups of the same nation met in the streets of Jeru- 

 salem and the result was disastrous to the Jews of the desert, for they 



