378 TYPHOID FEVER 



that, provided the needle be not too large, the procedure is quite 

 safe. Its use, however, is scarcely called for. 



(c) From the Urine. Typhoid bacilli are present in the 

 urine in at least 25 per cent, of cases, especially late in the 

 disease, probably chiefly when there are groups in the kidney 

 substance. For methods of examining suspected urine, see 

 p. 74. 



(d) 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 McConkey's lactose bile- 

 salt neutral-red agar, or in the other media described on pp. 

 47-53. After that period, though the continued infectiveness of 

 the disease indicates that they are still present, their isolation is 

 difficult. We have seen that after ulceration is fairly estab- 

 lished 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 correspondingly 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 

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

 many typhoid bacilli in the intestine. The microscopic examina- 

 tion of the stools is of course 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. The b. typhosus has, how- 

 ever, been isolated from water during epidemics. The b. coli is, as 

 might be expected, the organism most commonly present in such 

 circumstances. In the case of both bacteria, the whole series of culture 

 reactions must be gone through before any particular organism isolated 

 is identified as the one or the other ; probably there are saprophytes 

 existing in nature which only differ from them in one or two reactions. 

 In examining waters, the ordinary plate methods are generally used, but 

 the McConkey or similar media may be employed with advantage. 

 Klein filters a large quantity through a Berkefeld filter, and, brushing 

 off the bacteria retained on the porcelain, makes cultures. A much 

 greater concentration of the bacteria is thus obtained. From time to time 

 various substances have been used with the object of inhibiting the growth 

 of the b. coli without interfering with that of the b. typhosus. Most of 

 these have not stood the text of experience. Lately caffeine has been 

 used for this end. For use in examining waters the following is the 

 method employed : To 900 c.c. of the suspected water there are added 

 10 grammes nutrose dissolved in 80 c.c. of sterile water, and 5 grammes 

 of caffeine dissolved in sterile distilled water, heated to 80 C. and cooled 

 to 55 C. before addition. After mixing the ingredients there is added 

 10 c.c. of '1 per cent, crystal violet. The flask is incubated at 37 C. for 



