584 PROCEEDINGS OF SECTION I. 



if either there are few of these selected bacilli or if, when 9, large 

 number of non-lactose fermenting strains are isolated, we are not 

 inclined to be sparing of labour or media. With a sterile swab 

 for preference, we can inoculate from our unaffected lactose tubes 

 agar, glucose, mannitol, dulcitol, saccharose, and sorbitol litmus 

 peptone water. In 24 hours the sugars are read and the agglutina- 

 tion test done. A motile organism giving acid on glucose, manni- 

 tol and sorbitol, and not on dulcitol, lactose, and saccharose, and 

 giving a definitely positive agglutination reaction, can be safely 

 pronounced to be B. typhosus. To save media and labour, but 

 at the expense of time, when a large number of non-lactose fer- 

 menters are isolated, these can be first simply put on agar and 

 glucose and such organisms whose reactions agree upon these 

 can have the remaining sugars and fresh agar inoculated, and 

 next day one or more of those with typical reactions can have 

 its agglutination tested. If preferred the agglutination of all the 

 glucose fermenters can be done on the day earlier. 



As certain of the sugars are very expensive, there is a prac- 

 tical point in thus saving them worth bearing in mind when 

 extreme quickness is not of importance, as, indeed, for such pur- 

 pose it seldom is. Personally I regard attempts to short-circuit 

 delicate bacteriological tests with considerable disfavour, and feel 

 that though extreme rapidity may appeal to the dramatic instincts 

 of some, it is better to proceed carefully and cautiously. When 

 time is not of paramount importance I adopt the following scheme 

 whenever a large number of non-lactose fermenters are to be 

 examiiied : — 



Day I. — Plate on agar or MacConkey. 



Day II. — Pick off likely colonies, not less than 25, on to 

 lactose litmus peptone water. 



Day III. — Examine cultures and reject all showing acid or 

 acid and gas. The remainder are to be put on 

 glucose and agar. 



Day IV. — Reject all not giving acid on glucose—they are 

 fcEcalis alkaligenes type bacilli. Some or all of the 

 remaining cultures, which should be coliform bacilli 

 growing in a moist manner on agar, not affecting 

 lactose and producing acid on glucose, and, as a 

 rule, should be motile, can have their agglutination 

 reactions tested now, and be put on the remaining 

 sugars, or some or all be put in sugars leaving their 

 agglutination reactions till next day. 



