8 THE POPULAR SCIENCE MONTHLY. 



House, Croydon, June 5, 1882, he says : "I have abundance of evidence 

 that scarlatina is distributed by sewers, or rather that the germs which 

 grow it are conveyed with sewer-air. If, however, the constitution of 

 those receiving the germ is not fitted to grow it and to lead to its 

 fructification, no fever will arise, and the germs will abort. It will 

 not develop in ordinary flesh and blood, but requires that the recipient 

 should be iu a special state as regards his own blood to enable it to 

 mature." 



In addition to the evidence now presented, and which might be 

 greatly multiplied, as to the probability, or, as perhaps most phy- 

 sicians think, the certainty, that typhoid fever, diphtheria, and scar- 

 latina are thus caused or distributed from house to house, there is 

 the negative testimony presented in the fact that these three terri- 

 ble maladies are seldom seen in those Eastern Asiatic cities where 

 " modern improvements " in plumbing are unknown, and that with 

 us they have increased just in proportion to the extension of these 

 " improvements." 



It is quite probable, if not actually demonstrated, that Asiatic 

 cholera is often propagated in the same manner. The length of time 

 its germs survive after being thrown off from the body, and the estab- 

 lished fact that the excreta are known to contain and convey the 

 germs, increase the presumption that it may be distributed by the 

 sewers, if indeed it does not render it absolutely certain. 



Finally, no good reason can be given why every zymotic disease 

 may not in this manner, at certain times and under certain circum- 

 stances, be widely distributed, although no doubt the liability of such 

 distribution must depend much upon the viability of the germs and 

 upon other circumstances. 



What are the practical difficulties in the exclusion of sewer-gas where 

 plumbing is extensively distributed through our ^dwelling -houses / and 

 is there at present any ground of encouragement that they will be over- 

 come ? 



The Water- Traps. Profossor Doremus illustrated to the Academy 

 by experiment that gases would pass through water in water-traps, 

 although there was free ventilation on the opposite side. 



The applicability of these experiments to the question of the pas- 

 sage of sewer-gas and bacteria through water-traps has by some been 

 denied, and especially on the testimony of the experiments of Carmi- 

 chael, of Glasgow, in which experiments sewer-gases passed through 

 well-sealed and ventilated water-traps in only a small amount, and 

 bacteria were excluded altogether. 



I am not a chemist, and this question I prefer to leave with those 

 who are alone competent to decide it. 



Some experimenters, however, have not obtained the same results 

 as were obtained by Carmichael, Dr. Billings, and others. R S. G. 

 Paton, Ph. D., Chemist to the Health Department, city of Chicago, 



