258 Maj. Horrocks. Conditions under which " Specific" [Jan. 11, 



was poured inside each of them. The pipes were then rolled backwards and 

 forwards until the fluid was uniformly diffused over the inner surface of each 

 pipe. Twenty-four hours later the pipes, being perfectly dry, were fitted 

 together with clay joints so as to form the vertical pipe of fig. 3. Nutrose- 

 agar plates were then suspended in the pipe and sewage was allowed to flow 

 through the horizontal piping at a rate not exceeding 3 feet per second for 

 20 minutes. The plates were then removed and incubated at 22° C. 



At the end of 72 hours, all the plates were found studded with colonies of 

 B. prodigiosus. The experiment was repeated several times, and on each 

 occasion the same result was obtained. As the sewage passing through the 

 horizontal pipes did not contain B. prodigiosus, and control plates exposed to 

 the air were also free from this organism, it is fair to assume that the currents 

 of air produced by the passage of sewage through the horizontal pipes carried 

 up dried particles of B. prodigiosus detached from the walls of the vertical pipe. 



Group 3. — Experiments to determine whether Specific Bacteria are ejected 

 into the Air of Drains, Sewers, etc., from Sewage flowing under Normal 

 Conditions. 



In the first series of experiments, the trap of a 6-inch disconnecting trap 

 was filled with sewage, and two lengths of 6 -inch drain piping, having a 

 junction bend turned upwards, fixed at one end, were fitted horizontally into 

 the house side of the trap. Similar lengths of drain piping, but with the 

 junction bend turned downwards, were also fitted to the sewer side of the trap. 

 The vertical portion above the trap was lengthened by the addition of three 

 2-ft. lengths of 6-inch drain piping. The apparatus is shown in fig. 4. 



Fig. 4. 



