1894.] MICROSCOPICAL JOURNAL. 357 



oxygen on which its powerful antiseptic powers depend, and 

 consequenil}^ we find the commercial brands varying consider- 

 ably from their reputed strengths. The solution containing the 

 greatest percentage of available oxygen is the preparation known 

 as Marchand's, which, when perfectly fresh, is about a fifteen 

 volume solution. 



BACTERIOLOGY. 



A Co-operative Bacteriologic Investigation. — The com- 

 mittee on the Pollution of Water Supplies, of the American 

 Public Health Association in its report submitted at the meet- 

 ing id Montreal, Canada, September 25th last, suggested a co- 

 operative investigation by American bacteriologists into the, at 

 present, confused state of our knowledge on the important sub- 

 ject of the bacteriology of water supplies. The Association ap- 

 proved this suggestion and commended the efforts of the Com- 

 mittee in carrying out the work to the officers of State and mu- 

 nicipal boards of health, to the individual members of the As- 

 sociation, and to all persons interested in the purity of water 

 supplies, for such special assistance as they may be able to ren- 

 der. The proposition of the Committee was to the effect that 

 each laboratory willing to co-operate in the work devote itself 

 particularly to the investigation of a single so-called group or 

 species of water bacteria ; and that uniform standard culture 

 media be adopted, with the employment of these along the line 

 of a definite systematic scheme of laboratory work. The Com- 

 mittee when its membership is complete, will consist of those 

 participating in the work. In the meantime its organization is 

 in progress. — Journal American Medical Association. 



The Diphtheria Bacillus. — Strenuous efforts are being 

 made to correctly distinguish the virulent and non virulent 

 diphtheric bacilli. Morphologically they are identical, and find 

 a home in the throat of healthy people as well as those suffer- 

 ing from diphtheria. Bacteria from a healthy mouth and 

 throat are non virulent as a matter of course, while those taken 

 from an infected site naturally convey the poisonous virus. 



MICROSCOPICAL NOTES. 



Improper Use of The microscope. — The microscope has 



