76 THE POPULAR SCIENCE MONTHLY. 



result, for example, of a rapid flow along the drain into which the 

 waste-pipes discharge, and, under these circumstances, sewer-air and 

 its organic ingredients pass unhindered into our houses. So, also, traps 

 are liable to be forced by the pressure of the sewer-air upon them. 

 Having regard to some of Dr. Carmichael's experiments, it might at 

 first sight be supposed that organic particles contained in bubbles of 

 air would be detained in their passage through a water-trap. This, 

 however, is by no means the case. In certain experiments carried out 

 at the Royal Institution by Professor Tyndall, F. R. S., it was found 

 that air, passing through an experimental tube, carried with it " a con- 

 siderable amount of mechanically suspended matter." Dr. Carmichael 

 freely admits the inadequacy of water-traps as they exist, and points 

 out many dangers attendant upon them. He enforces the caution he 

 gives by a case related in a report of Dr. J. B. Russell, Medical Offi- 

 cer of Health for Glasgow. In certain tenements of one apartment, 

 having no connection with the sewer, there had been a death-rate from 

 diphtheria of 12, and from enteric fever of 24'9, per hundred thousand 

 inhabitants. The introduction of a sink increased the diphtheria 

 death-rate to 25*3 i. e., 110 per cent and from enteric fever to 67*7 

 i. e., 171 per cent the rate of mortality from certain allied diseases 

 also undergoing a corresponding increase. Not knowing whether there 

 were other circumstances that favored this special incidence of disease 

 upon these tenements, I should find some difficulty in asserting that 

 the drain-connection was the cause of the whole of the increase in the 

 diseases specified ; nevertheless, Dr. RusselPs opinion that it was, car- 

 ries great weight. 



One striking instance, which further illustrates this point, came un- 

 der my own cognizance. Some years ago I received instructions to 

 inquire into the cause of an outbreak of enteric fever in a small town- 

 ship in Yorkshire. The main incidence of the disease was upon a 

 group of houses, which formed an irregular square, containing twenty- 

 three cottages, occupied by eighty-eight persons. Up to the first 

 week in June the inhabitants of this locality had been free from fever, 

 but at that date a series of attacks of well-marked enteric fever oc- 

 curred almost simultaneously in a number of houses, fresh attacks tak- 

 ing place day by day until, in the space of a few weeks, one or more 

 inmates in fifteen out of the twenty-three cottages had been attacked, 

 the number of patients amounting to thirty-five. Now, when the con- 

 tagium of enteric fever is conveyed by water, the persons attacked are 

 generally attacked almost simultaneously. There is, however, in the 

 case of enteric fever, a definite interval, generally of some ten to four- 

 teen days, between the reception of the poison into the system and 

 the occurrence of symptoms of the disease. The water-supply which 

 these families generally used in common was a well in the neighbor- 

 ing field ; but this had been disused for a period which more than 

 covered the " period of incubation " above referred to. 



