SAFETY IN HOUSE-DRAINAGE. 



297 



gard to the passage of disease-germs through traps, and concludes 

 as follows : 



" The liquids in all these tubes and flasks, though kept from 

 two to five months at cultivation temperature, have remained 

 perfectly clear, and even when examined with a lens multiply- 

 ing nine hundred diameters, exhibited no trace of life. The con- 

 ditions of these experiments seem to me crucial, and to warrant 

 the conclusion that germs do not pass through a sound water- 

 trap. If no germs pass through, then it is certain that no parti- 

 cles pass through, because the particles in a soil-pipe are putrid, 

 and because the passage of organic particles through water neces- 

 sarily impregnates them with germs. 

 Clearly, therefore, such particles as 

 epithelium from the bowels in typhoid 

 fever, containing the typhoid contagia, 

 are cut off and effectually excluded 

 from the house by a sound water-trap. 

 Water-traps are, therefore, for the pur- 

 pose for which they are employed — 

 that is, for the exclusion from houses 

 of injurious substances contained in 

 the soil-pipe — perfectly trustworthy. 

 They exclude the soil-pipe atmosj)here 

 to such an extent that what escapes 

 through the water is so little in amount 

 and so purified by filtration as to be 

 perfectly harmless ; and they exclude 

 entirely all germs and particles, including, without doubt, the 

 specific germs or contagia of disease." 



The testimony of these distinguished scientists must be re- 

 garded as conclusive in the absence of contradictory evidence. Is 

 there such evidence on record ? Let us examine the authorities. 

 It is claimed that different results have been obtained in a few 

 instances by other investigators. Some years ago, Prof. Doremus 

 showed that gases would pass through water from one test-tube 

 to another. But it must be remembered that the gases used in 

 these experiments were in a highly concentrated form. Such 

 conditions as were then imposed are absolutely impossible outside 

 of the chemical laboratory. The atmosphere of sewers, drains, 

 and soil-pipes is in reality ordinary air containing less than one 

 X)er cent of the gases and particles given off by decomposing sew- 

 age. The results of over sixty analyses made by such men as Dr. 

 Letheby, Dr. Miller, of London, and the late Prof. Nichols, of Bos- 

 ton, show an average of only four tenths of one per cent of car- 

 bonic acid with mere traces of sulphureted hydrogen, marsh-gas, 

 and ammonia. The putrid organic vapors, and the putrefactive 



Fig. 3 



A Pot-Trap, sho-wing now 

 Water escapes by Sipuonage. 



