1893.] B MICROSCOrJCAL JOURNAL 117 



cover-glass. The slide, now containing a hanging drop cultiva- 

 tion, is tinned over. 



In such a drop the diatoms are in an almost natural state, and 

 their development and mode of lite may be watched under a 

 power as high as i-iS, though the lens commonly employed by 

 the author is a dry apochromatic with focal distances of 4 mm. 

 and N. A. 0.9s. In combination with^eyepieces 6, 12, 18, mag- 

 nifications of 373, 75O1 ''"*^^ 1 1^25 were obtained. 



The best part for observing the diatoms is the edge of the drop, 

 and this should be first centered under a low power. 



BACTERIOLOGY. 



Preparing Nutrient Bouillonj^for is, Bacteriological Pur- 

 poses. — Herren Petri and Massen in Arbeilcn aits d. Kaiserl. 

 Gestindheitsavitc^ viii. No. 3, give the following for preparing 

 bouillon : Fresh chopped meat containing little fat is soaked 

 for one hour in the necessary quantity of distilled water. It is 

 next heated for three hours at about 60"^ C, after which it is boiled 

 for half an hour and filtered. When cold the degree of acidity 

 of the fluid is tested from samples of 10-20 ccm. As a rule, 10 

 ccm. required by the litmus reaction 1.8 ccm. ; by the phenolph- 

 talein reaction, 3 ccm. of i-io normal caustic soda solution. The 

 broth obtained from the meat of different animals did not present 

 any striking differences. After the addition of alkali pepton and 

 soda it is boiled for some time, best over the open fire, for a 

 quarter of an hour, and then filtered hot. Too long and too fre- 

 quent boiling are to be avoided. The bouillon and the medium 

 prepared from it are to be kept in the dark. 



Degree of Alkalinity of Media for Cultivating Cholera 

 Bacilli. — Dr. M. Dahmen has reported in the Ce?itralbl. f. 

 Bakteriol. u. Pai-asitenk (1S92) the results of a series of experi- 

 ments to determine the most suitable degree of alkalinity for cul- 

 tivation media of cholera bacilli. From them he concludes that 

 for the examination of fseces for cholera bacilli a gelatin with 

 I per cent, of soda is the most suitable, and that a faintly alkaline 

 medium is not only not sufficient but absolutely unsuitable. 



Staining Flagella of Bacteria. — Herr L. Luksch finds that 

 by substituting ferric acetate for the sulphate of iron in the mordant 

 devised by Loeffler for staining bacterial flagella the disagree- 

 able deposit of the surface of the preparation is obviated. It is 

 certainly true that this deposit renders the original procedure less 

 effective in practice than the promise held out, and it is noted by 

 the author that Loeffler's solution should be made with ferric 

 and not with the ferrous salt, but if the acetate gets rid of the 

 surface deposit the distinction may be neglected. 



The author's solution is made trom freshly prepared coltl sat- 



