i 9 4 INFECTION AND IMMUNITY 



It is now recognised by physicians that " mem- 

 branous croup " is due to the diphtheria bacillus, and 

 is in fact a form of diphtheria, most common in very 

 young children, in which the larynx and larger 

 bronchial tubes are the seat of infection. 



The total number of deaths reported from diph- 

 theria in the last census year (1900) was 28,959. 

 This amounted to 29 in every 1000 deaths from all 

 causes. This is a very considerable gain upon the 

 proportion shown by the census of 1890 (49.7 per 

 1000). The death-rate per 100,000 of the population 

 was 45.2 ; in 1890 it was more than twice as great 

 (97.8). This gain is no doubt largely due to the 

 diminished mortality resulting from the specific treat- 

 ment of the disease with diphtheria antitoxin. The 

 death-rate is more than twice as great in cities as 

 in rural districts. The District of Columbia has the 

 highest rate (75.4) ; and the State of Vermont the 

 lowest (18.3). It is evident that, in view of our 

 previous statement that the mortality is greater 

 in cities than in rural districts, it is not fair to com- 

 pare the District of Columbia with States having a 

 large rural population. As compared, however, with 

 the average rate for cities (52.8) the record of the 

 capital city of the nation is not creditable. It is due 

 to the large coloured population of the city and 

 the comparatively large death-rate among negroes as 



