METHODS OF EXAMINATION. 327 



stroke cultures on agar. tubes, made from it at once. It is 

 better, however, to put a quantity into a sterile test-tube and 

 centrifugalise it. The upper part is then drawn off with a 

 pipette, and cultures made as above from the lower part or 

 from the slight deposit which sometimes forms. 



(c) From the Stools. During the first ten days of a case 

 of typhoid fever, the bacilli can be isolated from the stools 

 by the ordinary plate methods preferably in phenolated 

 gelatine. After that period, though the continued infective- 

 ness of the disease indicates that they are still present, their 

 isolation is practically hopeless. We have seen that after 

 ulceration is fairly established by the sloughing of the 

 necrosed tissue, the numbers present in the patches are much 

 diminished and therefore there are fewer cast off into the 

 intestinal lumen, and that in addition there is a correspond- 

 ingly great increase of the B. coli, which thus causes any 

 typhoid bacilli in a plate to be quite outgrown. From the 

 fact that the ulcers in a case of typhoid may be very lew in 

 number, it is evident that there may be at no time very 

 many typhoid bacilli in the intestine. We may add that the 

 microscopic examination of the stools is useless as a means 

 of diagnosing the presence of the typhoid bacillus. 



Isolation from Water Supplies. A great deal of work 

 has been done on this subject. It is evident that if it 

 is difficult to isolate the bacilli from the stools it must 

 a fortiori be much more difficult to do so when the latter 

 are enormously diluted by water. Some have held that the 

 typhoid bacillus has never been isolated from suspected 

 water, and have adduced this as an argument against its 

 etiological relationship to the disease. The considerations 

 just advanced, however, militate against such a view. The 

 B. typhosus has been isolated from water during epidemics. 

 This was done by Klein in the outbreaks in recent years at 

 Worthing and Rotherham. The B. coli is, as might be ex- 

 pected, the organism most commonly isolated in such circum- 

 stances. In the case of both bacteria, the whole series of 

 culture reactions must be gone through before any particu- 

 lar organism isolated is identified as the one or the other ; 



