314 THE POPULAR SCIENCE MONTHLY. 



of soil-pipes, which matter they are constantly decomposing into 

 gases and soluble products readily washed away. They are also 

 present in large quantities in sewage as it flows in the sewers. 



There are a few forms of bacteria which we have good reason 

 to believe are the causes of certain diseases called specific. Each 

 of these specific diseases has a definite course, and is due to the 

 entrance into the body of particles of living matter derived, 

 directly or indirectly, from the body of a person affected with the 

 same disease. 



We now know the particular kinds of bacteria which cause 

 several of these diseases, and can identify them with considerable 

 certainty. Those of most interest in connection with house-drain- 

 age are those which are supposed to cause suppuration, septicae- 

 mia, puerperal fever, erysipelas, intestinal irritation and diarrhoea, 

 typhoid fever, and sore throats and diphtheria. 



These diseases are less frequent and less fatal in sewered than 

 in unsewered cities, and in the central sewered portion of a city 

 than in the unsewered suburbs. Systematic house-to-house in- 

 spections in cities have shown that over one half of the houses 

 have more or less defective and foul fixtures and leaky soil-pipe 

 joints, so that if specific germs are often present there should be 

 much more sickness than there is. As a matter of fact there is 

 no evidence that scarlet fever, measles, small-pox, or whooping- 

 cough has ever been transmitted by sewer air. There is reason to 

 think that in a few and exceptional cases diphtheria and typhoid 

 have been caused by inhaling sewer or soil-pipe air ; but the dan- 

 ger of incurring these diseases in this way is small as compared 

 with the other and usual sources of origin, although it is prob- 

 able that the ordinary non-specific sore throats which sewer air 

 tends to produce form a specially favorable site for the develop- 

 ment of the specific microbe of diphtheria, and that in this way 

 foul air is a predisposing cause of this disease. Schools are much 

 more dangerous than sewers as regards the propagation of diph- 

 theria. 



The typhoid-fever bacillus is said to have been found in the 

 air of a sewer from an institution in which there was an epidemic 

 of typhoid, and there is a theoretical possibility that the disease 

 might thus be produced in a house by conveyance of its germs 

 through sewer and soil-pipe air ; but such conveyance must be 

 extremely rare. It should be distinctly understood that neither 

 the most perfect system of house-drainage nor total absence of 

 house-drainage will protect the inmates of the house to any con- 

 siderable extent from diphtheria or from typhoid. 



The most dangerous micro-organisms which are commonly 

 found in sewer and soil-pipe air are those which produce suppura- 

 tion, erysipelas, or septic poisoning when they gain access to the 



