ZOOLOGY AND BOTANY, MICROSCOPY, ETO. 
C93 
Other methods are given, for which wo must refer tho student to the 
original. 
Spermatogenesis.* — In investigating the part which central cor- 
puscle and sphere play in forming the spermatozoon, Herr C. Messing 
got best results with Hermann’s platinum chloride-osmio-acetic acid 
mixture, .and similar mixtures used by G. Messing, e.g. 25 parts 10 per 
cent, platinum chloride, 20 parts 2 per cent, osmic solution, 5 parts 
glacial acetic acid, and 50 parts distilled water or concentrated aqueous 
solution of corrosive sublimate. 
Dilute Sulphuric Acid in Preparing Fish Skeletons.! — Dr. 0. Thilo 
recommends the following procedure for preparing fish skeletons. Wash 
the fish thoroughly with soap and brush, leave for a day in water, immerse 
in a cooled mixture of English sulphuric acid and water (1 : 10), and 
leave for 8—10 days. Then cleaning is easy. To remove the sulphuric 
acid, place in water (once changed) for 12 hours, then in soda solution 
(1 : 30) or in saturated baryta hydrate. The cartilage becomes a beauti- 
ful white colour. In 4-5 weeks the branchial skeleton falls apart. If 
this is to be avoided, 8 days in the baryta solution will suffice. A skull, 
like that of the sturgeon, should remain about three weeks in tho sul- 
phuric acid solution. To avoid any softening of tho skeleton, 70 to 80 
per cent, alcohol may be used instead of water. The cleaned cartilages 
may be placed in 30-50 per cent, alcohol, or in Wickersheimer’s solution, 
for a couple of weeks, and then kept dry in securely closed glass vessels. 
Demonstrating the Structure of the Human Heuroglia4 — Prof. 
C. Weigert devotes no inconsiderable portion of an elaborate monograph 
on the normal human neuroglia to the methods necessary for demon- 
strating its structure. The general course of procedure was to take 
small pieces of central nervous system, which should be quite fresh and 
of “ good consistence,” and immerse them for eight days in a fluid having 
mordant and fixative properties. This was composed of formalin, neutral 
acetate of copper, and chrome-alum. The pieces were then got ready for 
section by the celloidin method. The sections were then treated with 
reducing agents, i.e. permanganate of potash, chromogen, and sulphurous 
acid solutions. The next step was to increase the staining affinity of 
tho neuroglia by means of an aqueous solution of chromogen. The 
sections were stained by the fibrin method. 
The mordant-fixative is composed of 5 per cent, neutral acetate of 
copper, 5 per cent, acetic acid, and 2’5 per cent, chrom-alum in water. 
To make this solution, it is necessary first to dissolve the chrom-alum in 
boiling water, then add the acetic acid, and lastly the finely powdered 
copper salt. If made in any other way there is a copious green pre- 
cipitate. 
Reduction is effected by immersing the sections for about 10 minutes 
in * 33 per cent, solution of permanganate of potash ; they are now care- 
fully washed in water, and then, the water having been poured away, the 
reducing solution is poured in. This fluid is made by dissolving 5 per 
cent, chromogen and 5 per cent, formic acid in water and filtering. To 
90 ccm. of this solution 10 ccm.. of a 10 per cent, solution of ordinary 
* Arch. Mikr. Anat., xlviii. (1898) pp. 111-42 (2 pis.). 
t Anat. Anzeig., xii. (1898) pp. 244-7. 
X Abhandl. d. Senckenb. Gt s., xix (1895) pp. 65-213 (13 ids.). 
1896 3 b 
