BY R. GREIG SMITH. 743 



he has modified the method to ensure the growth of Bact. typhi. 

 Instead of taking for further examination the turbid bouillon 

 containing the greatest number of drops of phenol solution, he 

 takes the tube next lower in order; on the other hand, to obtain 

 Bact. coli commune he uses the tube containing most disinfectant. 

 The details of the method are here given briefly. 



Hankin's modification. — -To five tubes each containing 10 c.c. 

 of ordinary nutrient bouillon are added 0, 1, 2, 3 and 4 drops of 

 Parietti's solution and a few drops of the suspicious water. A 

 water which contains comparatively few bacteria is filtered 

 through a procelain candle and the microbes upon the porcelain 

 surface brushed into a few c.c. of sterile water, which is used for 

 infecting the bouillon. The tubes are incubated for 24 hours at 

 37°; at the end ©f this time an observation is made and one of 

 the series is taken for further cultivation. The turbid tube con- 

 taining the greatest number of drops of disinfectant is discarded, 

 excepting when Bact. coli commune is sought for. Generally the 

 turbid tube next in order is taken unless it has a thick scum 

 upon the surface, or it has a growth visible only in the deeper 

 layers of the liquid, or when bubbles of gas are apparent in the 

 medium. In the latter cases the choice should fall upon a tube 

 which is uniformly turbid. The tube that is taken is used to 

 start a fresh series of bouillon cultures, the lowest member of 

 which has the same number of drops of Parietti's solution as the 

 tube taken. The process of selection is repeated upon these 

 tubes after a 24 hours' incubation. A third series may be pre- 

 pared, but usually one of the second series is used for making a 

 smear culture on a fairly dry agar slope. Any suspicious colonies 

 that grow on the sloped surface are inoculated into litmus-agar 

 tubes and further examined. 



Hilbert* criticised Hankin's method unfavourably, so far as it 

 relates to the separation of Bact. typhi. He found that drops of 

 a typhi suspension prepared by diluting a 24 hours' bouillon 



•Hilbert, Centralblatt fur Bakt. 1 Abt. xxvii., 520. 



