492 BACTERIOLOGY. 



maintained (p. 179). The acidity of this gelatin is such as 

 to inhibit the development of the B. icteroides. 



It has been proposed to utilize the fact that the typhoid colony 

 tends to give off delicate fibrils from its'periphery, whereas the border 



of the colon bacillus is sharply defined. To normal urine which has 

 been allowed to stand for a couple of days till the reaction is alka- 

 line, 0.5 per cent, of pepton and 3-5 per cent, of gelatin are added. 

 The mixture is heated in the water-bath for an hour, filtered, filled 

 into tubes and sterilized. This is done by steaming- for 15 and 10 min- 

 utes on the first and second days, respectively. 



Within 24 hours at 22 the colon colonies appear as round, yellow- - 

 ish, finely granular and sharp bordered bodies, whereas the typhoid 



colonies are surrounded by whorls of threads. In this way, it is said 

 to be possible to readily detect the typhoid bacillus in the urine or 

 f eces of the patient. 



Stoddart's Medium. 



The Eberth bacillus, as a rule, is more motile than the 

 colon bacillus. This fact may be used to good advantage 

 in distinguishing 1 between these organisms. Direct micro- 

 scopical examination or the staining of flagella will not give 

 a satisfactory indication of the motility. If, however, a 

 soft medium is used, the motile organism will rapidly 

 diffuse throughout the medium or over its surface, whereas 

 the non-motile organism forms a thick, white, non-spread- 

 ing growth. 



A liter of meat extract is prepared in the usual way 

 (p. 153); 10 g. of pepton and 5 g. of NaCl are added, and the 

 mixture slightly warmed till solution results. It is then 

 divided into two equal portions. 



To one portion, 10 per cent, of gelatin is added, and, 

 when this has been dissolved, the liquid is titrated with 

 & NaOH. An excess of 10 c.c. of N NaOH per liter is ad- 

 ded to impart the desired alkalinity. This and the subse- 

 quent procedure is exactly the same as that described on 

 p. 155. 



