64 



THE AMERICAN MONTHLY 



[April, 



Date. 



Jan. 8.. 



" II.. 

 Feb. 4.. 



" 8.. 



" I5-- 



" 22.. 

 Mar. 2. 

 - " 10. 



" 16. 



" 18. 



" 25- 



Apr. I.. 



" 6.. 



3321 

 4228 

 3151 

 1997 

 3225 

 1772 



3459 

 1069 

 38, 

 338 

 806 

 2033 

 2961 



Remarks. 



very turbid. 



becomes clear. 



very turbid, 

 (heavy rains). 



From these figures it will be seen 

 that on March 18 the comparatively 

 clear water, owing to continued dry 

 weather, contained about 338 bac- 

 teria. Soon after, heavy, prolonged 

 rains brought the water into a very 

 turbid condition and the number of 

 bacteria rose quickly to 2961. 



It will also be observed that the 

 number of germs which liquify the 

 gelatin does not necessarily grow 

 larger with the increase of the total. 

 They are most abimdant proportion- 

 ately in the clear water and are pre- 

 sumably the natives of the water, the 

 other bacteria being washed in by the 

 rains from decaying vegetation. 



From one city pump 600 bacteria 

 in I c.c. were obtained. From 

 another two examinations gave re- 

 spectively 3,163 and 857 bacteria. 

 The slightly turbid water of the Poto- 

 mac is therefore more trustworthy 

 than the very clear water of these 

 pumps. It is quite probable that 

 the wooden barrel of these ancient 

 structures contributes a fair quota to 

 the whole number in the water. 



How these figures should be inter- 

 preted remains a very delicate question 

 until water from a large variety of 

 sources shall have been examined. 

 The application of this method is still 

 in its inlancy and premature conclu- 

 sions can only bring it into discredit. It 

 now becomes necessary to furnish for 

 it a practical basis by examining what 

 we consider the best as well as the 

 poorest waters according to a strictly 

 uniform process. In this connection 



the carefully weighed words of the 

 author of this method might be of 

 service. It being questioned at the 

 last cholera conference at Bei^lin as to 

 what he considered good water. Dr. 

 Koch* said : — 



' A large number of micro-organ- 

 isms indicates that the water has 

 received admixtures in a state of de- 

 composition and loaded with micro- 

 organisms, impvu-e tributaries, etc., 

 which might contribute, in addition 

 to the many harmless bacteria, also 

 pathogenic forms, that is, infectious 

 matter. . . . Experience thus far has 

 shown that in good waters the num- 

 ber of germs capable of development 

 varies between 10 and 150. As soon 

 as the number considerably exceeds 

 this limit, thew^ater must be suspected 

 of receiving contributions from pol- 

 luted sources. If the number reaches 

 or exceeds i ,000 I should not permit 

 its use as drinking water, at least not 

 in times of a cholera epidemic. The 

 number 1,000 is chosen by me as ar- 

 bitrarily as has been the case in se- 

 lecting the limiting values in chemi- 

 cal analysis, and I allow each one to 

 change it according to his convic- 

 tions.' 



A Method of Mounting Several 

 Gronps of Small Microscopic Ob- 

 jects Under one Cover. 



The following directions for mount- 

 ing pollens will sufiice for other small 

 objects : 



The pollens should be gathered 

 from freshly opened flowers, and may 

 be teased from the anthers with a 

 needle into small bottles, which, after 

 the pollen is thoroughly dry, should 

 be kept corked. 



Prepare a card marked with three, 

 four or five spots, all arranged within 

 the limits of a three-fourths of an 

 inch cover-glass, place a glass slip 

 upon the card, and put a minute drop 

 of turpentine on the slip over one of 

 the marked spots. A needle with a 

 little turpentine on it will serve to 



♦Deutsche Med. Wochenschrift, 1885, Sept. 12. 



