304 BACTERIA AND DISEASE 



the anomalous position of the bacteriologist who sets to work to 

 examine a water suspected of typhoid pollution three weeks 

 previously. There can be no doubt that these three difficulties are 

 very real ones. The solution to the problem will be found in the 

 dictum that " a water in which sewage organisms have been detected 

 in large numbers should be regarded with suspicion " as the vehicle of 

 typhoid, even though no typhoid bacilli are discoverable. The chief 

 of these sewage bacteria are believed to be Proteus vulgaris, Bacillus 

 coli, Proteus Zcnkcri, and Bacillus enteritidis sporogenes. 



It may occur to the reader that, as the typhoid bacillus is, as far 

 as we know, comparatively common, drinking water may frequently 

 act as a vehicle to carry the disease to man. But, to appreciate the 

 position, it is desirable to bear in mind the following facts. The 

 typhoid bacillus is found, with other bacteria, in the excrement of 

 patients suffering from the disease ; it is short-lived ; in waters there 

 exist organisms which can exert an influence in diminishing its 

 vitality ; it is, so to speak, enormously diluted in waters ; exposure 

 to direct sunlight destroys it; and it has a tendency to be carried 

 down stream, or in still waters settle to the bottom by subsidence. 

 Even when all the conditions are fulfilled, it must not be forgotten 

 that a certain definite dose of the bacillus is required to be taken, 

 and that by a " susceptible " person. 



Epidemic Diarrhoea 



By "epidemic diarrhoea" (zymotic or epidemic enteritis) is meant 

 a specific disease, which may be defined as an acute infective 

 disease, affecting chiefly children Under two years of age, occurring 

 during the summer months in epidemic form, and characterised by 

 the occurrence of diarrhoea, vomiting, and wasting, accompanied in 

 severe cases by toxsemia and collapse. The disease is a large 

 contributor to infant mortality, and in many urban districts it is 

 the most serious of all infant diseases, if measured by fatality. 



The exact cause of epidemic diarrhoea is not at present known. 

 In 1887 Ballard formulated certain propositions which have 

 obtained general acceptance. They are as follow : 



" That the essential cause of diarrhoea resides ordinarily in the 

 superficial layers of the earth, where it is intimately associated in 

 the life-processes of some micro-organism not yet detected or 

 isolated. 



" That the vital manifestations of such organism are dependent, 

 among other things, perhaps principally upon conditions of season 

 and on the presence of dead organic matter, which is its pabulum. 



"That on occasion such micro-organism is capable of getting 

 abroad from its primary habitat, the earth, and having become air- 



