1907.] Bacteria may be present in Ventilating Pipes, etc. 263 



.south-east corner of the block there is a similar disconnecting chamber (C), 

 which receives the drainage from a w.c. in the basement and is also connected 

 to the Europa sewer. There are six inspection chambers, with ventilating 

 covers at the road level, and a 6 -inch ventilating pipe on the Europa sewer, 

 between the Centre Block and the Europa Pass Barracks, a distance of some 

 200 yards (see Plan of hospital drainage). Plates were suspended in the top 

 of the hospital soil pipe, at the north-east corner, some 30 feet above the 

 junctions of the w.c.'s, in the disconnecting chambers (A), (B), and (C), in all 

 the inspection chambers connected with the Europa sewer and in the top of 

 the ventilating pipe of the sewer. A rich emulsion of B. prodigiosus was then 

 placed in each of the pans of the w.c.'s, which were then flushed. Twenty- 

 four hours later the plates were removed and incubated at 22° C. After 

 48 hours, all the plates, except those in disconnecting chamber (A), were 

 iound studded with colonies of the special organism employed. Plates 

 exposed on the ground close to the Centre Block for 24 hours were also 

 incubated, but no signs of the B. prodigiosus appeared in them. 



Judging by the results obtained with the experimental installations, it was 

 expected that the special organism would be found in the hospital soil pipe, 

 disconnecting chamber (B), and in the chambers and ventilating pipe of the 

 sewer. But as the disconnecting chamber (C) at the south-east corner of 

 the Centre Block is not in any way connected with the w.c.'s receiving the 

 emulsion of the B. prodigiosus, and is separated from the Europa sewer by a 

 modern disconnecting trap, the special organism should not have appeared in 

 this chamber. The experiment was repeated again three times, and, in 

 addition to the places already mentioned, plates were also suspended in the 

 disconnecting chambers (U) and (E) connected to the east side of the South 

 Block. The plates were left in situ for 24 hours, and then incubated as 

 before. Colonies of B. prodigiosus appeared in the same places as in the 

 previous experiment, but none were found in the chambers (D) and (E). 



It was then evident that there must be some means by which the discon- 

 necting chamber (C) was placed in communication with the Europa sewer. 

 A careful examination of the bottom of the chamber was made, and it was 

 found that there was no plug in the cleaning arm of the disconnecting trap ; 

 consequently, the chamber was in direct communication with the air in the 

 sewer. Plugs were found firmly fixed in the cleaning arms of the discon- 

 necting traps in the chambers (D) and (E), and prevented micro-organisms in 

 the sewer air from entering the chambers. 



The cleaning arm in the chamber (C) was then firmly plugged and the 

 experiment repeated. The result was that colonies of B. prodigiosus appeared 

 in the plates placed in the hospital soil pipe and in the chamber (B), but none 



