ZOOLOGY AND BOTANY, MICROSCOPY, ETC. 
481 
with screws, a rubber band interposing ; while the agar mixture is being 
prepared in a steamer, autoclave, or over the open fire, the plate is 
gently warmed with a Bunsen’s burner, and when ready the agar 
mixture is poured on to the plate (or pan b) through the funnel opening e. 
The centrifuge is set in motion, and the burner removed. In about 
half an hour the agar is cooled and set, and on examining the contents of 
the pan it will be found that the agar is perfectly clear, all the particles 
Fig. 74. 
f-§ 
e 
^ * 
n 
l 
■ r 
having been sedimented in a layer of 2-3 mm. at the periphery. It only 
remains to cut off the sedimented layer to obtain a mass of perfectly 
clear agar, which is then distributed into test-tubes, &c. 
There are two points of importance in the manipulation : the first is 
that the pan should be thoroughly warmed before the agar is poured in ; 
and the second, that when this is done, the centrifuge should be 
made to work up as fast as possible, otherwise the agar may be slightly 
opalescent. The centrifuge used by the author is Iiunne’s (fig. 73). 
Preparation of Mallein.* — Herren Fr. Hutyra and H. Preisz prepare 
mallein in the following way. After the virulence of the glanders 
bacilli has been considerably increased by repeated transferences through 
guinea-pigs, cultures are made on potatoes in capsules. When the 
cultures and the potatoes have become quite dry and black they are 
placed in a glass vessel and just covered with a fluid composed of equal 
parts of distilled water and glycerin and 3-5 per cent, chloride of 
mercury. After having been incubated for 10-14 days at 37°*5, the 
mixture is filtered and then steam sterilised for an hour. The fluid 
obtained is dark brown, but there is no connection between darkness of 
colour and intensity of action. For one dose 0*3-0 *5 ccm. sufficed, 
and this the authors diluted with 0*5 per cent, carbolic acid up to 
3*0 ccm. 
Bacteriological Examination of Water. y — Herr G. Marpmann 
points out that for practical purposes the bacteria in water may be divided 
into two great classes, pathogenic and sewage bacteria. The patho- 
genic include the typhoid bacilli, pyogenic cocci, and the cholera vibrio ; 
* Centralbl. f. Bakteriol. u. Parasitenk., l te Abt., xvii. (1895) p. 341. 
t Tom. cit., pp. 362-7. , 
