1907.] Bacteria may he present in Ventilating Pipes, etc. 259 



Three litmus-lactose-rmtrose-agar plates were next suspended with the 

 media facing upwards in the vertical pipe by means of wire cages, the 

 uppermost plate being about 6 feet 9 inches above the sewage in the trap. 

 Three gallons of sewage, taken from a main sewer in Gibraltar, were then 

 inoculated with a rich emulsion of the B. typhosus, and poured down the bend 

 on the house side of the trap. The sewage passed through the apparatus at a 

 rate not exceeding 3 feet per second, and was received in a bucket placed 

 under the bend on the sewer side of the trap. The inoculated sewage was 

 passed through the trap in the same manner on two successive days for about 

 half an hour. The plates were then removed and incubated at 37° C. for 

 24 hours, when numerous transparent blue colonies resembling those of the 

 B. typhosus were seen in each plate. Several of the colonies were tested with 

 anti-typhoid serum (horse) diluted 1 — 100 and, agglutination occurring at 

 once, the colonies were planted out on agar slopes. The growths thus 

 obtained were examined as to morphology and Gram staining, and then 

 planted out in the usual media. The following results were obtained : — 



Medium. Result of incubation at 37° C. 



Glucose-peptone Acid, no gas. 



Lactose-peptone Unchanged. 



Maltose-peptone Acid, no gas. 



Cane-sugar peptone Unchanged. 



Starch-peptone Unchanged. 



Neutral red Unchanged. 



Litmus-milk Very faint acidity, no clotting. 



Peptone-water No nitroso-indol reaction. 



Potato Colourless growth. 



Proskauer and Capaldi, No. 1 No growth. 



Gelatine Thin transparent growth, medium not 



liquefied. 



Nitrate-broth Reduced to N0 2 . 



Morphology, etc Small motile bacillus. 



Gram staining Decolorised. 



The bacilli were agglutinated by an anti-typhoid horse serum diluted 

 1—500. 



A portion of the agar growth derived from one colony was then emulsified 

 in water and injected subcutaneously into a guinea-pig. As a control, a 

 similar emulsion of the B. typhosus used to inoculate sewage was injected into 

 a second guinea-pig of approximately the same weight. At the end of three 

 weeks the sera of both guinea-pigs agglutinated, in a dilution of 1 — 100, the 

 stock culture of B. typhosus. 



It is plain that in this experiment the B. typhosus was ejected from the 

 sewage to a height of 6 feet 9 inches. 



