IIO BACTERIOLOGICAL METHODS 



The following is offered by way of fuller explanation of some 

 of the details of the method above outlined for the isolation and 

 identification of the Bacillus typhosus. The unusually active 

 motility of the typhoid germ has been utilized by several in- 

 vestigators (Drigalski and Starkey) as a means for separating 

 it from less highly motile forms. Drigalski allowed from 5 to 

 10 liters of the suspected water to stand in tall milk cans for i or 

 2 days at the room temperature, after which he plated definite 

 amounts taken from the surface of the container into litmus- 

 lactose-agar. By this method he was enabled to isolate typhoid 

 bacilli from several contaminated springs. Starkey used glass tubes 

 bent into four loops which after being filled with phenol broth were 

 inoculated at. one end and incubated anaerobically at 37 C. for 

 24 hr. The more actively motile typhoid bacilli found their way 

 to the fourth loop from which they were isolated by plating. The 

 centrifugal method above recommended is merely an adjunct to 

 the methods employed by Drigalski and Starkey. The non- 

 motile bacteria are thrown down first and in a very short period 

 of time thus being an advantage over the Drigalski method in 

 which gravity is the separating force. It is true that in time the 

 motile forms would also be thrown down. It is therefore im- 

 portant not to prolong the centrifugalizing more than is necessary. 

 In place of the four-loop Starkey tube we would suggest the use 

 of four separate tubes; one a simple U-tube or single-loop, a W- or 

 double-loop, a three-loop and a four-loop tube. These tubes, after 

 being cleaned and sterilized are filled with phenol broth and in- 

 oculated at one end at the same time. Incubate at 37 C. or even 

 at 40 C. and examine loopfuls taken from the ends opposite the 

 ends inoculated as follows: The U-tube at the end of 6 hr., 

 the double-loop tube and the three-loop tube at the end of 12 hr., 

 the three-loop tube (reexamination) and the four-loop tube at the 

 end of 24 hr., and the four-loop tube again at the end of 36 hr. 

 if necessary. The phenol broth and the higher temperature hinders 

 the growth of most bacteria without checking the growth of the 



