604 



SUMMARY OF CUEBENT RESEARCHES RELATING TO 



Fig 



substituted for a tube. The flask is conical, and holds about half a litre, 

 and is fitted with a two-holed indiarubber stopper. Through one hole 

 passes the " entrance tube " A A, a glass tube about 8 in. long, and 

 having an internal diameter of 3/8 in. It reaches about two-thirds of 



the way down the flask, and is closed at 

 the outer end by a glass stopper B fitted 

 on with a piece of indiarubber tubing. 

 Into the other hole of the stopper is 

 fitted the "exit tube" C C. This is a 

 piece of glass tubing (1/4 in. diameter) 

 bent round at the lower end, so that it 

 opens in the neck of the flask just under 

 the rubber stopper. It is open at both 

 ends, but contains two cotton-wool plugs 

 to prevent entrance of any micro-organ- 

 isms from the outside. 



Ten ccm. of Koch's pepton-gelatin 

 are introduced into the flask, and the 

 stopper tied on with copper wire. The 

 flask is then steamed for an hour at 

 100° C, and on cooling, an even layer 

 of gelatin is distributed over the bottom. 

 In taking a sample of air the aspi- 

 rator is attached to the exit tube C, and 

 the rubber tube and stopper B removed 

 from A. A known volume of air is then 

 drawn through the flask, after which the 

 stopper is replaced. The microbes settle 

 on the jelly, and having developed into 

 colonies, may be counted in a few days. 

 Counting may be facilitated by marking 

 out the bottom of the flask in squares. The rate of aspiration adopted 

 was 1 litre in three minutes. In order to prove the safety and certainty 

 of this method, various tests, for which the original must be consulted, 

 were applied. 



The authors consider that their method is extremely safe, and 

 possesses all the advantages and none of the disadvantages of Hesse's and 

 Frankland's methods. 



Value of Bacteriological Examination for Estimating the Purity 

 of Drinking-Water.* — In a short review of the present condition of 

 the question as to how far the bacteriological examination of water is of 

 value in estimating its purity, Dr. Ordmann sums up very shortly the 

 results of his own and others' experiments. It may be remembered that 

 when plate cultivations were first used for the breeding of micro- 

 organisms, much was expected of this method for determining the 

 quality and characters of micro-organisms present in a given specimen 

 of water. This expectation was not fulfilled, for it was found on the 

 one hand, in water chemically good, that not unfrequently there were 

 large quantities of micro-organisms present ; and on the other, that in 

 water chemically bad, it very frequently happened that but few micro- 

 organisms developed. So that the author, while not depreciating the 



* Zoilschr. f. Naturwiss., Ixi. (1888) pp. 654-8. 



