ZOOLOGY AND BOTANY, MIOROSCOPY, ETC. 561 



The necessary apparatus consists of: — (1) A short-necked four- 

 ounce flask, fitted with a caoutchouc stopper through which two tuhes 

 pass ; they are bent at right angles, and have their external ends 

 drawn out ; (2) a tube with a bulb (about 25 ccm. capacity) blown on 

 the side, and the ends tapering to fine points ; (3) a long combustion- 

 tube 18 in. long, loosely packed for 10 in. with asbestos, which can 

 be connected with a refrigerator. About 50 ccm. of Pasteur's solution 

 are boiled in the flask, the combustion-tube is heated to, and kept at, 

 a red heat, a slow current of air is passed through, the flask is attached, 

 and the tubes are sealed up while the sterilized air is passing and the 

 solution is boiling. A bulb-tube is sealed up at one end, distilled 

 water is introduced and boiled off, and the other end is sealed up 

 while the tube is full of aqueous vapour ; one end is now broken off 

 under the surface of the water to be examined, and when the bulb is 

 full the end is immediately sealed up again. The heated combustion- 

 tube is now connected with the refrigerator, and a rapid current of air 

 passed to clear the apparatus ; one end of the bulb-tube is connected 

 by means of indiarubber tubing with the refrigerator, which is now 

 cooled ; the other by a similar connection with one of the flask-tubes ; 

 all the ends are broken by pressing the indiarubber connections, and 

 the water from the bulb-tube rushes into the partially vacuous flask, 

 followed by the cooled sterilized air ; the flask-tube is then sealed up 

 and placed in a convenient place for the development of the organisms, 

 and the apparatus disconnected. All requisite precautions are taken 

 to avoid the admission of extraneous organisms. 



Removal of Microbes by Filtering.* — M. C. Chamberland finds 

 that a filter composed of porous unglazed porcelain will entirely free 

 any fluid from the microbes which it may contain. It is cleaned with 

 the greatest ease by heating. 



Effect of Prolonged Repose and Filtration through Porcelain 

 on the Purity of Water.f —Prof. H. Fol and M. P. L. Dunant 

 describe experiments on this subject. Struck by the small number 

 of germs in the water of the Lake of Geneva compared with that of 

 other drinking waters, and attributing it to the repose of the water, 

 the authors resolved to test this theory. Impure water, estimated to 

 contain not less than 150,000 germs per ccm,, was allowed to stand, 

 and after eight days it was found that it had lost 94 per cent, of the 

 germs, only one in seventeen remaining in suspension. At the end 

 of fifteen days 23 per cent, more had sunk to the bottom, making 

 95*3 per cent, for the three weeks. 



Water that had been passed through Chamberland's unglazed 

 porcelain filters was found to be quite sterile, and the authors con- 

 sider that not only water, but any liquid sufficiently fluid to pass 

 through the porcelain under a pressure of from two to three atmo- 

 spheres can thus be sterilized cold. 



Determination of the Number of Germs in Air. — Prof. H. Fol 

 writes that he now constantly employs curved tubes closed at one end 



* Comptes Eendus, xcix. (1884) pp. 247-8. 

 t Arch. Sci. Phys. et Nat., xiii. (1885) pp. 110-8, 

 Ser. 2.— YoL. V. 2 O 



