264 Maj. Horrocks. Conditions under which " Specific" [Jan. ll r 



appeared in the plates suspended in chamber (C), proving conclusively that, 

 the patent cleaning arm had been the channel through which the B. prodigiosus 

 entered this chamber in the previous experiments. 



As a control of the above experiments, plates were next placed in the 

 inspection chambers connected with the west end of Centre and South Blocks. 

 The contents of these chambers are removed by a separate drain, which 

 passes along the west of the hospital into the disconnecting chamber (F) r 

 close to the south gate of the hospital. No colonies of B. prodigiosus were 

 found in any of the chambers, although the plates were treated precisely as 

 in the previous experiments. A fortnight later the experiment was repeated, 

 but on this occasion the pan of a w.c. connected with the drain on the west 

 side of the hospital was inoculated with B. prodigiosus, and the w.c.'s on the 

 east side were left in their natural condition. The result was that colonies 

 of the special organism appeared in the plates placed on the west of the. 

 hospital, but none were found on the east side. 



In all the above experiments the plates were left in the chambers and soil 

 pipes for 24 hours, consequently the B. prodigiosus might have resulted from 

 dried particles of the growth separated from the walls of the pipes and 

 chambers and carried upwards by air currents, as well as from the bursting of 

 bubbles and ejection of droplets from the flowing sewage. In order to 

 determine whether the separation of dried particles was the source from which 

 the bacteria were obtained, the experiments were repeated, but on these 

 occasions the plates were withdrawn as soon as the w.c.'s had been flushed, 

 each experiment only taking 20 minutes. When incubated the plates 

 showed practically as many colonies of the B. prodigiosus as in the previous 

 experiments, showing that special bacteria may appear in the air of the 

 chambers and pipes independently of the separation of dried particles. 



It might be objected that in the experiments just related the bacteria were 

 suspended in water and had no organic matter adhering to them such as would 

 be the case under natural conditions. When faecal material is flushed down 

 w.c.'s and carried through a drainage system, it is probable that the B. coli and 

 the B. typhosus in the case of typhoid stools, will have an organic envelope 

 which may materially affect the results. 



In order to ascertain whether the objection raised had any force, plates of 

 litmus-lactose-nutrose-agar were suspended in the ventilating pipe of the 

 Centre Block for 24 hours and then incubated. All colonies having a reddish 

 tint were fished and carefully studied, the result being that typical members 

 of the coli group were readily isolated. Plates were also suspended in large 

 inspection chambers connected with one of the main sewers of the town, about 

 10 feet above the flowing sewage. The plates were removed at the end of 



