PREVENTIVE MEDICINE AND THE WAR 335 



don, is really not an exception. On the second map it also 

 should be moved to this region (see footnote to Table 3.) 

 Lewis is the only real exception. Why did the soldiers from 

 this great north-eastern section of the United States bear the 

 camp diseases of the winter of 1917-18 better than those from 

 other sections of our country? Are they physically superior 

 men? No, the draft records show their physical inferiority. 

 Moreover, the per cent, of rejections in the draft was larger 

 in this section than in either the South or West. There is one 

 answer to this question and it is to my mind quite satisfactory. 

 The diseases which caused the greatest number of deaths in our 

 camps during that winter were the acute respiratory diseases 

 already mentioned and which we may properly denominate 

 " Crowd diseases." The section designated is the most densely 

 populated part of our country, and a larger proportion of the 

 men coming from it had acquired a greater degree of resistance 

 to these diseases than was possessed by their more rural com- 

 rades. Before mobilization of the army the pneumonias, as 

 the vital statistics show, were urban diseases, reaping their 

 greatest harvests in the crowded cities. Those who had lived 

 under urban conditions had acquired a degree of immunity 

 not possessed by those who had never come in contact with the 

 bacteria which cause these diseases. 



While difference in susceptibility to the acute respiratory in- 

 fections influenced the death rate between divisions, it was 

 equally in evidence among the organizations of the same 

 division. 



Camp Cody reports that disease incidence was 48 per cent. 

 higher in the I34th Infantry than in the I33rd. The latter was 

 made up of troops from the larger cities of Iowa. The former 

 included troops mainly from the smaller towns of Nebraska. 



Similarly, disease incidence was 51 per cent, greater in the 

 1 36th Infantry made up from the smaller towns of Minnesota 

 than in the I35th Infantry made up of men from the larger 

 cities of this State. 



The excess among rural troops of such diseases as measles, 



