ZOOLOGY AND BOTANY, MICROSCOPY, ETC. 
399 
rubber plug. The tube b reaches nearly to the bottom of the flask while 
its upper end is expanded. Over the expansion fits the glass cap c, the 
free end of which is plugged with cotton-w< 
termed an aeroscope The bottom of the flask 
is covered with a layer of nutritive medium 
composed of 10 grm. bouillon containing 20 per 
cent, gelatin. The apparatus and its contents 
having been sterilized in the usual way, the 
gelatin bouillon layer is covered with a similar 
bulk of sterilized bouillon. The tube b almost, 
but not quite, touches the solid layer. 
A known volume of air, say 10 litres, is 
drawn through the apparatus by attaching an 
ordinary pump at a. The air bubbles through 
the liquid medium and deposits its germs there. 
The two nutritive layers are then melted to- 
gether by placing the flask in warm water; 
after which plate or rod cultivations can be 
made, or what is better, the whole mass may 
be left in the flask. In the last case the rubber 
stopper should be replaced by a cotton-wool 
plug. From the author’s experiments made 
with this apparatus he determined that the atmosphere at an altitude of 
1000 metres is extremely pure. 
Absence of Phosphorescence in Cholera Cultures.* — In the course 
of some experiments made for comparing the cholera vibrio with other 
organisms having some resemblance to it, Dr. Kutscher remarked that 
two cultivations were distinguished by a strong greenish-white phos- 
phorescence. Further observations made on material from various 
sources such as water, dejecta, &c., established the fact that no incon- 
siderable number of these vibrios were endowed with phosphorescence, 
but that in the cholera vibrio this was absent. The optimum temperature 
for phosphorescence was found to be about 22° C. Hence the absence 
of phosphorescence may occasionally be found useful as a negative 
criterion in the diagnosis of cholera. 
Preparation of Nutrient Medium for Bacteria from Eggs.| — In 
Koch’s original method of employing eggs there was the disadvantage 
that there was a want of uniformity in the composition of the medium ; 
this has been overcome by Dr. Wesener who mixes the yolk and albumen 
by shaking the egg before boiling ; when the egg has been well shaken 
it should be placed in water at 75° to 80° C. for 1/2 to 3/4 of an hour. 
It is then transferred to sublimate solution for cooling and for steriliza- 
tion of the surface ; after drying with sterilized wool the shell and its 
membrane are removed, when the contents are seen to be of a uniform 
golden-yellow colour. Three or four slices are cut with a sterilized 
knife, placed in Esmarch’s dishes, and sterilized as usual. Among the 
advantages of this medium are its alkaline reaction, its richness in 
albumen, and the fact that it is unfavourable to the growth of moulds. 
* Centralbl. f. Bakteriol. u. Parasitenk., xv. (1894) pp. 44-6. 
+ Centralbl. f. Allgem. Path., Jan. 1894 ; see Brit. Med. Journ., No. 1736, 1894, 
p. 56. 
This apparatus is 
Fig. 32. 
