ZOOLOGY AND BOTANY, MICROSCOPY, ETC. 
447 
gelatin as a medium for tlie bacteriological examination of water, and 
merely on the ground that it does not liquefy, he recommends it. The 
medium should contain 1 per cent, of agar, and care must be taken that 
the water in the water-bath in which the agar tubes are placed is 
heated up to 38°-40° before any considerable quantity (e.g. 1 ccm.) of 
water is added. Instead of diluting germ-full water with germ-free water, 
he prefers to use only so little water that not more than 200 colonies 
develop on one plate ; and in order to avoid mistakes incidental to this 
method, two at least control plates are made. Cold capsules must be 
previously heated in the incubator. The plates should be kept turned 
face down, as this position delays drying considerably, and also has other 
advantages. Four tables giving the results of observations made with 
Dresden water seem to confirm the author’s statements. 
Fixation and Staining of Cytoryctes vaccinae.* — Dr. v. Wasielewski 
inoculated the cornea of 50 rabbits and 10 guinea-pigs with vaccine lymph, 
and, by staining with alum-fuchsin-hasmatoxylin and alum-fuchsin, was 
able to recognise the appearances which have been described by Guarnieri 
and others. The bodies are held to be parasitic in nature, and have 
been named Cytoryctes vciccinse. In the 25 illustrations the parasite is 
depicted as lying within the nuclear membrane and without the chromatin 
network. The parasites vary in number and size. The fixatives used were 
chromic acid sublimate (saturated solution of sublimate 200 + water 250 
+ chromic acid. 0*5), picric acid sublimate (saturated aqueous solution 
of picric acid 1000 -f- saturated solution of sublimate 1000 -f- glacial 
acetic acid 50 + water 2000), picric-acetic acid, Flemming’s fluid, sub- 
limate, and sublimate-nitric acid (equal parts of 3 per cent, nitric acid 
and saturated solution of sublimate in hot physiological salt solution). 
The sections were stained with alum-fuchsin for 24 hours (fuchsin 1, 
alum 3, water 100), and then decolorised with bichromate of potash (a 
mixture made immediately before use, of equal parts of 0 • 5 per cent, 
solution and 70 per cent, alcohol. The sections were then washed in 
distilled water and after-stained with Ehrlich’s haematoxylin. 
(3) Cutting-, including Imbedding and Microtomes. 
Proper Angle of Microtome Knife.f — Dr. B. Rawitz adduces expe- 
rimental proof to show that the microtome knife should be placed at an 
acute angle rather than at a right angle. When placed at the latter 
angle, the sections, according to their thickness, are always more or less 
crowded together, thus distorting the finer structures of the tissues cut. 
The experimental proof consists of the measurement of the sections cut 
with the knife at a right angle and also at an angle of 45°. The sections 
were made from a block of paraffin measuring 20 J by 11 J mm., and 
were 15, 10, and 5 /x thick. With the knife at the acute angle they all 
measured 11 mm. in breadth, while with the knife at a right angle they 
measured 9^ mm. for 15 /x, 9 mm. for the 10 fx, and 8 mm. for the 5 y. 
sections, thus showing a shrinkage of 2, 2^ and 3 mm. respectively. 
Technique of Celloidin Serial Sections.! — The procedure recom- 
mended by Dr. J. Tandler for the manipulation and treatment of series 
* Centralbl. Bakt. u. Par., lte Abt., xxi. (1897) pp. 901-13 (1 pi.), 
t Anat. Anzeig., xiii. (1897) pp. 65-80. 
t Zeitschr. f. wiss. Mikr., xiv. (1897) pp. 36-8. 
1897 2 i 
