Vlll PROCEEDINGS. 



The bacteriological examination of sewer air has not received 

 the attention which should have been given to it, and possibly we 

 have in our own ranks members who,, by research and investigation, 

 can throw some light on this important question. Within the last 

 few years improved methods for investigating air-borne bacteria, 

 especially Streptococci, have been introduced, but they have not yet 

 been applied to sewer air, and when it is borne in mind that 

 Streptococci are the most abundant organisms in sewage, that they 

 are amongst the most important of disease-producing bacteria, and 

 that some at least of the diseases to which sewer air is credited with 

 giving rise, are in all probability strepcococcal infections, it is 

 plain that the examination of sewer air for Streptococci should 

 prove an important field of investigation. 



Improved methods have also been recently introduced whereby 

 the common intestinal bacteria belonging to the B. coli group 

 (including the typhoid bacillus) may be much more easily identi- 

 fied and isolated. 



The first step taken by Dr. Andrews was to endeavor to find 

 sewage organisms in the sewer air, and he succeeded in finding an 

 organism which was not the true B. coli communis, but was identi- 

 cal with a characteristic sewage member of the group, present in 

 the sewage to the number of at least 30,000 per c. c. 



The most important experiments, however, were those relating^ 

 to Streptococci:, and Dr. Andrews established the fact that the 

 Streptococci of the sewer air are very different from those of the 

 fresh air outside the sewers, and in the very point in which they 

 differ from those of the fresh air they tend to approach those of 

 the sewage. The importance of this discovery cannot be' over- 

 estimated, and it is fairly obvious that the whole future disposition 

 of sewer ventilation or sewer air treatment may depend upon the 

 facts which further examination in this direction will produce. 



The question arises, what effect does this variation in the con- 

 stitution of Streptococci have upon the human constitution? Both 

 Dr. Andrews and Dr. Hurtley remained in the sewers for long 

 periods and it is not recorded that they suffered at all; in fact, 

 Dr. Hurtley specifically states that he did not experience the slight- 



