BAGTERIA IN WATER 695 



or of other species probably emanating from contaminating sources, 

 such as a B. coli. Unfortunately there are no rehable methods by which 

 typhoid and cholera germs can be isolated from water with any degree 

 of regularity or certainty. Although frequently the isolation of such 

 organisms is possible, a negative result in these cases is by no means 

 eliminative of their presence. 



The isolation of typhoid bacilli from water is very difficult, chiefly 

 because of the great dilution which contaminations undergo upon enter- 

 ing any large body of water. The difiiculty of isolating typhoid bacilli, 

 even from the stools of infected patients, makes it clear that such diffi- 

 culties are enhanced when a considerable dilution of the excreta takes 

 place. Furthermore, water is by no means a favorable medium for the 

 typhoid bacillus. Russell and Fuller ^ have shown that typhoid bacilli 

 may die in water within five days, and it is unquestionable that the 

 rate of increase of these bacteria is by no means equal to that of many 

 other microorganisms for which polluted water at the temperature en- 

 countered in streams and lakes forms a much more favorable medium. 



It is thus clear that even in infected waters the niunber of typhoid 

 bacilli encountered can never be very great.^ 



A large niunber of methods for the isolation of the typhoid bacillus 

 from water have been devised. Most of the media used are identical 

 with those employed for the isolation of these bacteria from the stools. 

 These media have been discussed in the chapter dealing with the tj^hoid 

 bacillus. 



Drigalski ' has reported a method for which he claims considerable 

 success in isolating typhoid bacilli from water, which depends upon the 

 motility of the organisms. One- to two-hter samples of water are taken 

 and allowed to stand at room temperature in high jars for one or two 

 days. Small quantities are then removed from the surface and planted 

 on Wurtz's lactose litmus agar. The method depends upon the probabil- 

 ity of the settling out of non-motile organisms and the possibility, there- 

 fore, of getting motile organisms only in the plates. 



Parietti* and others have attempted to eliminate other organisms by 

 adding phenol and hydrochloric acid to neutral broth, in the hope that 

 the high acidity and the antiseptic qualities of the phenol will destroy 

 more delicate organisms than the typhoid bacillus. Inasmuch as B. 



' Russell and Fuller, Jour. Inf. Dis., Suppl. 2, 1908. 



^ Laws and Anderson, Rep. of Med. OflSoer, London County Council, 1894. 



' Drigalski, Arb. a. d. kais. Gesundheitsamt, xxiv, 1906. 



* Parietti, Rev. d'igiene e san. pub., 1890. 



