260 ATMOSPHERE IN RELATION TO HUMAN LIFE AND HEALTH. 



Permeability of soil to air, moisture of soil not excessive, average soil 

 beat at 6 feet deep about 79°, a moderate amount of contained organic 

 matter, aud little putrefaction or ordinary decomposition ; mean annual 

 temperature of air about 72° F. The minimum water level, otherwise 

 the maximum of soil ventilation, and the maximum of cholera coincide. 

 Dry or saturated soil are unsuitable for the continuous growth of the 

 bacillus. 



DIARRHEA. 



In an inquiry conducted about thirty-five years ago 1 regarding the 

 X^revalence of diarrhea, a disease which in England is fatal to very 

 large numbers of children, it was found that there are districts in 

 which endemic diarrhea is unknown, and others in which it prevails 

 extensively every year. The excess of mortality coincided in all cases 

 with one of two local conditions, the tainting of the atmosphere with 

 the products of organic decomposition, especially human excrement, or 

 the habitual drinking of impure water. Since the time of the report a 

 large amount of evidence has accumulated which goes to prove that 

 summer or infantile diarrhea is caused by the infection of air and 

 food by emanations from a damp organically contaminated soil raised 

 above a certain temperature. Houses built on or near a subsoil con- 

 taining decomposing organic matter, or where sewers leak, are particu- 

 larly subject to diarrhea. The nature of the soil is important. Sand, 

 loose fine gravel, deep mold, and permeable soils generally, where 

 organic matter is abundant, are productive of the disease ; houses built 

 upon rock, without fissures, are generally altogether exempt. "Made 

 ground," containing organic rubbish, on which so many houses in the 

 outskirts of large towns are built, emits products of decomposition into 

 the interior of houses and is a fruitful source of suffering. The prac- 

 tice of building on rubbish heaps should be made a criminal offense. 

 The absence of free ventilation within aud around houses greatly 

 increases the mortality from this cause. Deep drainage has been fol- 

 lowed by a marked fall in the prevalence of the disease. Paving, 

 impervious flooring in houses, cleanliness in the storage of food, with 

 ventilation, are important measures for its reduction. Purity of air, 

 indeed, in this as in so many other cases, is the remedy to be sought. 



Diarrhea in the epidemic form arises under conditions very similar 

 to those of cholera. It' may be in fact a very near relation of that 

 microorganism, but is milder in its effects and has the quality of 

 developing at lower temperatures. When polluted, damp soil at 3 or 

 4 feet deep reaches about 56° to 60° C, as it generally does in England 

 in June or July, the cases of diarrhea mount up rapidly, for the diar- 

 rheal microbe is then multiplying in the subsoil and emerging through 

 the upper stratum, and may indeed be developed in decaying organic 

 matter on the surface. Settling upon articles of food and drink, such 

 as vegetables, water, and milk, it multiplies and develops the poison 



1 .Second Report to the Privy Council, London, 1859. 



