3? 8 Profs. Percy Frankland and Marshall Ward. 



' Wiener klinische Wochenschriffc,' 1888 ; Centralbl. f. Bakteriol.' 

 vol. iv, 1888, p. 467) states that out of 2000 samples of water which 

 he had examined bacteriologically, there were only five in which he 

 was able to detect typhoid bacilli. 



From the above it will be seen that many investigators, since the 

 year 1886, claim to have discovered the typhoid bacillus in potable 

 waters, but, in the majority of cases, these discoveries, especially the 

 earlier ones, must be accepted with considerable reserve, as, until 

 recently, it was customary to rely for the identi6cation of the typhoid 

 bacillus on altogether insufficient data, as it only gradually became 

 understood that there are several other forms presenting the closest 

 points of resemblance in their morphological characters, both micro 

 and macroscopic, to the typhoid bacillus, with which they are not 

 unfrequently associated, and, moreover, some of these simulatory 

 forms are of very frequent occurrence in natural waters. Indeed, even 

 at the present day, the identification of particular forms or " species " 

 of bacteria is in a transitional and highly unsatisfactory state, as it is 

 daily becoming clearer that the characters, both morphological and 

 physiological, of one and the same micro-organism are often liable to 

 the profoundest modifications through changes of environment and 

 other causes, whilst there are almost daily being discovered in nature 

 new forms which differ only from already well-known forms or 

 " species " in what appear to be the most minute, trifling, and insig- 

 nificant particulars. 



Tinder these circumstances, it is practically certain that some of 

 the bacilli discovered in water, and believed to have been typhoid 

 bacilli, must, in reality, have been only forms closely simulating the 

 more striking characters of the typhoid bacillus. On the other hand, 

 it is equally certain that a great many waters which have been sub- 

 mitted to examination for typhoid bacilli may have contained them 

 without their being discovered, for, as will be pointed out later, the 

 ordinary method pursued in the bacteriological examination of water, 

 in which a few drops, or at most a cubic centimetre or two, of the 

 water is submitted to plate cultivation, can only, under the most 

 exceptional circumstances, lead to the detection of typhoid bacilli. 



Thus, whilst there is considerable evidence that the typhoid bacilli 

 have been found on a number of occasions in waters which had been 

 convicted of distributing typhoid amongst their consumers, the 

 failure to discover these bacilli in other waters equally guilty need 

 excite no surprise when the very imperfect methods of examination 

 which are commonly employed for their discovery are taken into 

 consideration. 



In connection with the above discoveries of typhoid bacilli in pot- 

 able water, I will only at this stage further remark that, in by far 

 the majority of cases, the waters accused of containing these bacilli 



