CONDITIONS FAVOURABLE TO DIARRHOEA 367 



extent. (3) Towns having the water-carriage system of sewage 

 have as a rule much less diarrhcea than those retaining other 

 methods of removal of excrement. (4) Towns with the most 

 perfect scavenging arrangements have the least epidemic diarrhoea. 

 (5) The influence of the soil is a decided one. Where the dwelling- 

 houses of a place have as their foundation solid rock with little 

 or no superincumbent loose material, the diarrhoeal mortality is, 

 notwithstanding many other unfavourable conditions and sur- 

 roundings, low. On the other hand, a loose soil is a soil in which 

 diarrhceal mortality is apt to be high. (6) Given two towns 

 equally placed, so far as social and sanitary conditions are con- 

 cerned, their relative diarrhoeal mortality is proportional to the 

 height of the temperature and the deficiency of rainfall of each 

 town, particularly the temperature and rainfall of the third quarter 

 of the year." 



Dr Newsholme concludes that "the fundamental condition 

 favouring epidemic diarrhoea is an unclean soil, the particulate 

 poison from which infests the air and is swallowed, most commonly 

 with food, especially milk." In other words, epidemic diarrhoea is 

 a so-called " filth-disease " preventable by improved sanitation in 

 the broadest meaning of the term.^ 



Summary. — From the facts and suggestions quoted above, and 

 they are but representative of many other similar views receiving 

 the general support of epidemiologists, it will be evident that at 

 the present time the cause of epidemic diarrhoea is to be found in 

 four conditions, which may be expressed shortly as two proposi- 

 tions, thus : (i) Epidemic diarrhoea is a bacterial disease; (2) Its 

 occurrence depends, wholly or partly, upon surrounding tempera- 

 ture, deficiency of rainfall, and pollution of food, chiefly milk. 

 The exact relationship which these conditions have to each other 

 is not known. Some authorities hold that a certain temperature 

 affects food, conducing towards creating in it injurious properties. 

 Others believe that it is a question of pollution of milk by dust, 

 which carries to the milk the causal micro-organisms, and that 

 deficient rainfall favours this contamination, and increased tempera- 

 ture favours the growth and multiplication of the bacteria thus 

 conveyed to the milk. As Dr Newsholme says, " Whatever be its 

 mode of operation, a frequent fall of rain during the summer 

 weeks, even though its total amount be not great, is one of the 

 most effectual means of keeping down the diarrhoeal death rate" ;2 

 and whilst he considers temperature conditions of great import- 



^ Public Health, 1899-1900, voL xii., pp. 139-213. 

 ^ Annual Report on Health of Brighton, 1902, p. 48. 



