ZOOLOGY AND BOTANY, MICROSCOPY, ETC. 
707 
white commercial gelatin sold in thin flakes. After filtering through 
fine cloth about 30-40 ccm. of glacial acetic acid and a gramme of per- 
chloride of mercury are added. 
The object of these additions is to keep the gelatin liquid and also to 
preserve it- At the ordinary temperature, 15°, it has the consistence of 
thick syrup. According to the season and the temperature it is easy to 
modify these proportions. 
The object to be sectioned is placed first of all in this gelatinous 
solution diluted with twice or thrice its volume of pure water. It is 
afterwards immersed in the thick gelatin solution, a little of which has 
been poured into a paper box. The mass is then set by placing the 
paper box and its contents in a crystallizer and then carefully pouring 
round it some spirit. If alcohol should be unsuitable other hardening 
agents such as picric acid, bichromate of potash, &c., may be substituted, 
but these reagents act more slowly than spirit. 
When sufficiently firm the mass may be sectioned in the usual way 
and the sections mounted in gelatin or glycerin, or be freed from the 
gelatin imbedding by dissolving it in water. 
(4) Staining- and Injecting. 
Methylen-blue Staining of Nervous System of Invertebrata.* — - 
Herr O. Burger, when investigating the nervous system of Nemertine 
worms, seems to have obtained very good results, judging at least from 
the coloured illustrations said to be faithful representations, by injecting 
these animals with a fluid made by dissolving O’ 5 grm. methylen- 
blue in 100 grm. of 1/2 per cent, cooking salt solution, or with a simple 
watery solution of the same strength. Sea water, in which methylen- 
blue is imperfectly soluble, is quite unsuitable for the purpose. The 
injections were made frequently, one injection imparting only a faint 
staining. The best period for injecting was in the half-dead condition, 
or in that state when the animal or parts thereof still show signs of life. 
The time required for bringing about good injection results was at 
least 6-8 hours, and sometimes much longer. After a time the author 
found that satisfactory results were more easily obtained by merely 
injecting a part or organ. The preparations were fixed with dilute 
picrate of ammonia, and afterwards put up in glycerin to which a trace 
of ammonia had been added. 
The staining does not last very long, and hence in examining a 
specimen it is advisable to begin at those parts from which the blue 
colour first disappears, viz. at the periphery. 
Permanent Preparations by Golgi’s Method.| — Dr. G. C. Huber 
finds that permanent preparations of nervous tissue stained by Golgi’s 
method can be obtained in the following manner : — The pieces are to be 
hardened and silvered according to the procedure advised by Bamon y 
Cajal and von Kolliker, and celloidin sections cut up under 95 per cent, 
spirit. The sections are then immersed for 15 minutes in creosote and 
then transferred for some minutes to turpentine. After this they are 
* Mittheil. Zoologiscli. Station zu Neapel, x. (1891) pp. 206-54 (2 p.’s.), 
t Anat. Anzeig., vii. (1892) pp. 587-9. 
