SURVIVAL OF BACILLUS TYPHOSUS 363 



in tanks of sea- water, after nine, sixteen, and even eighteen 

 days from the commencement of the experiment, the 

 oysters showing no abnormal condition. 



As regards the vitality of the Bacillus typhosus in sewage 

 we have little certain information ; probably it tends to 

 die out within a few days. In sterilised sewage inoculated 

 with it the B. typhosus hardly multiplies at all, and at 

 the end of ten days has died out. Certain organisms in 

 sewage seemed to have a deleterious action on the B. 

 typhosus, hastening its extinction, viz. the B. fluorescens 

 Uquefaciens and B. fluorescens stercoralis. Russell and 

 Fuller, subjecting the bacillus to the direct action of 

 sewage, found the survival to range from three to five 

 days. 



In dry garden earth, according to Dempster, 1 the Bacillus 

 typhosus does not live longer than eighteen days (Firth 

 and Horrocks recovered it up to twenty- five days), and 

 in peat it dies within twenty-four hours. In moist soil, 

 however, the bacillus still survived on the forty-second 

 day. In an artificially dried soil it was not found alive 

 after the seventh day. 



Sidney Martin found that in moist sterilised soil kept at 

 temperatures from 3 to 37 C., the B. typhosus maintains 

 its vitality for upwards of fifteen months, but that in 

 unsterilised soil it rapidly dies. 2 



Mair 3 concludes that the typhoid bacillus can survive 

 in natural soil in large numbers for about twenty days, and 

 is still present in a living condition after seventy to eighty 

 days, but that there is no evidence that it is capable of 

 multiplying and leading a saprophytic existence in ordinary 

 soil. He suggests that Martin's result (the rapid extinc- 

 tion of the bacillus in unsterilised soil) may be explained 



1 Med.-Chir. Trans., vol. Ixxvii, 1894, p. 263. 



2 Reps. Med. Off. Loc. Gov. Board for 1896-1901. 



3 Journ. of Hygiene, vol. viii, 1908, p. 37. 



