192 APPLIED BACTERIOLOGY 



lent Klebs-Loffler bacilli have been occasionally met with by 

 several investigators in the normal throats of apparently 

 perfectly healthy individuals. 



Distribution and Occurrence. — Diphtheria seems to be dis- 

 tributed more or less widely all over the globe, but is far 

 more prevalent in cold and temperate climates than in the 

 tropics. It is one of those few diseases in which a distinct 

 increase (which cannot be attributed entirely to improved 

 diagnosis) has taken place in the past few years. Some 

 twenty-five years ago the disease was far more prevalent 

 in rural districts than in towns, but during the past few 

 years, while it has decreased in rural, it has increased in 

 urban districts. Its tendency to reappear at intervals in 

 particular districts would point to the specific organism 

 having either a saprophytic tendency, or to its retaining 

 its vitality in dust, and thus rendering the site of previous 

 cases more or less permanently infective. 



Professor Smith, in a recent report for the School Board 

 of London, states that in his opinion elementary schools do 

 not play so great a part in the dissemination of diphtheria 

 as is usually supposed, and he proves this point by the 

 collection of a mass of statistics dealing with cases which 

 have come under his notice as Medical Officer of the School 

 Board. In no case, he says, has it been necessary to order 

 the closure of the school on account of the outbreak of diph- 

 theria. Accompanying his report are a series of coloured 

 maps, illustrating the prevalence of diphtheria in each county 

 during the past six years, which go to show that diph- 

 theria has, for some reason which we do not at present 

 understand, become concentrated in the neighbourhood of 

 Middlesex. 



Its distribution does not appear to be affected by other 

 diseases; its mortality is highest during the last quarter, 

 and lowest in the summer months. There is no evidence 



