66 



24 hours in this polluted water the oyster had taken in 800 

 B. coli communis. After a further day only 150 were found 

 in the next oyster, and after having been transferred to clean 

 water they practically cleared themselves in two further 

 days. The previous experiment has shown us that the sea 

 water per se is capable of materially reducing in 48 hours the 

 number of B. coli communis, and, therefore, the reduction 

 of this microbe in the oysters after 48 hours from 800 to 

 150 is what we might expect. This experiment is in so far 

 interesting, as it appears to point to this, viz., that clean 

 oysters are capable of dealing promptly with the B. coli 

 communis of sewage, seemingly more promptly than with 

 the B. coli communis directly derived from human faecal 

 matter. 



SEEIES D, 



In the following series of observations, an attempt was 

 made to differentiate those microbes of sewage and of fecal 

 matter which in Drigalski plates are capable of forming 

 " blue " colonies that is, colonies that might interfere with 

 and aggravate the diagnosis and recognition of the colonies 

 of B. typhosus and similar microbes of a pathogenic character 

 like the B. enteritidis Gaertner, both of which would indicate 

 specific pollution ; the former being derived from the typhoid 

 patient (bowel discharge, urine), the latter from the bowel 

 discharges of a person affected with certain forms of acute 

 gastro-enteritis, and most probably also with the acute ailment 

 called paratyphoid, recognised now as different from typhoid 

 fever. The microbe of this disease, viz., the Bacillus para- 

 typhosus appears from all accounts to closely resemble the 

 B. Gaertner, being possibly a variety of this latter. 



The B. Gaertner forms blue-violet colonies on Drigalski 

 medium at 37 C., but they grow slower, coming up slower and 

 remaining smaller than those of B. typhosus, and are marked 

 also from the latter by showing a central opaque spot. By 

 microscopic examination in the hanging drop, by subculture 

 in neutral red broth andin litmus milk, in MacConkey fluid, and 

 by the agglutination test with typhoid serum, the differential 



