914 



SCIENCE. 



[N. S. Vol. XII. No. 311. 



this subject is studied by many water an- 

 alysts who do not attempt general species 

 determinations, and to the further fact that 

 upon these topics opinion is more crystal- 

 lized than upon the general subject of species 

 methods. 



Relative to fermentation tests, this topic 

 was considered at length by the Bacterio- 

 logical Committee in the Report of 1897. 

 The present status with reference to those 

 recommendations may be outlined as fol- 

 lows : 



In the preparation of fermentation solu- 

 tions, the use of meat infusion as compared 

 with meat extract is still an open question. 

 Both are used. Opinion seems unanimous, 

 however, that in either case they should 

 contain no muscle sugar. It is generally 

 considered that a reaction of 1.5 per cent, 

 acid is not perfectly satisfactory, and most 

 workers employ solutions which are prac- 

 tically neutral to phenolphthalein. The 

 amount of sugar is 1 per cent, as a rule, as 

 recommended, although it appears that glu- 

 cose is used by many to the exclusion of 

 lactose and saccharose. This latter tend- 

 ency would seem to be a step in the wrong 

 direction, for many lines of work. Opinion 

 is at variance concerning the effect of heat 

 upon these sugars in the course of the 

 preparation of the solutions. Cultivations 

 are made almost invariably at 37 degrees 

 C. for a period of three days, with records 

 daily as to the percentage of gas in the 

 closed arm. In other particulars there are 

 some diiferences in general practice, but 

 they apparently are of little consequence in 

 affecting results such as would be obtained 

 by strict adherence to the procedures of the 

 1897 Report. 



While considerable increase to our knowl- 

 edge of the fermentation-produced bacteria 

 has occurred within the past three years, 

 there is not at present suflBcient evidence at 

 hand to recommend an improved set of pro- 

 cedures. 



With regard to the isolation of B. coli 

 communis, there are evidently quite a 

 number of procedures which are used with 

 success. These procedui-es differ somewhat 

 on account of the wide range in natural 

 conditions under which tests are made for 

 this form in various waters. Where B. coli 

 communis forms a small percentage of the 

 total bacteria, the custom appeai-s to have 

 come into general use of employing a pre- 

 liminary incubation to eliminate ordinary 

 water bacteria. It is thought that it will 

 not be a laborious task during the coming 

 year to draft a graded series of acceptable 

 methods to cover the wide range of condi- 

 tions met with in practice. 



It is gratifying to note a general uni- 

 formity in the characteristics considered 

 essential to the identification of B. coli 

 communis, as follows : 



1. Fermentation of dextrose with the 

 production of carbonic acid equal approxi- 

 mately to 33 per cent, of the total gas 

 formed. 



2. Coagulation of milk. 



3. ISTon-Iiquefaction of gelatine, with 

 growth at the surface and in the form of 

 beads along the line of inoculation in a 

 gelatine tube-culture. 



4. Formation of indol. 



5. Conformity to the main morphological 

 characteristics of this tj'pe as published. 



With reference to those forms resem- 

 bling B. coli communis, which ferment 

 sugars with the production of carbonic 

 acid varying widely from 33 per cent, of 

 the total gas, it is now generally regarded 

 that they should not be reported as B. coli. 

 What their true relation is to this species, 

 and what their sanitary significance is rela- 

 tive to the character of waters in which 

 they are found, are questions which cannot 

 be answered satisfactorily at present. 



Very few, if any, experienced bacteriolo- 

 gists engaged in public health work make 

 a practice of attempting to isolate the ty- 



