276 SUMMARY OF CURRENT RESEARCHES RELATING TO 



C. Golgi,* in studying the peripheral and central nervous fibres 

 of the spinal cord, exposes the nerves to the action of osmic acid, 

 chromic salts, and silver nitrate, according to certain methods of 

 combination. For example, a nerve is removed with care from a 

 freshly killed animal (rabbit), and placed in a mixture of 10 parts of 

 a 2 per cent, solution of potassium bichromate with 2 parts of 1 per 

 cent, osmic acid solution. After about an hour the nerve is divided 

 into emiller pieces of ^ to 1 cm. in length, and again jilaced in the 

 solution, where it is left some hours longer (it must be examined every 

 3 hours), and finally is placed for not less than 8 hours in 0*5 per 

 cent, solution of nitrate of silver, and then mounted in dammar 

 varnish in the ordinary way. Better preparations are produced by 

 placing nerves which have been exposed — in the case of peripheral 

 nerves 8 hours, of central nerves 10 to 15 days — to the action of 

 bichromate of potash, then from 12 to 24 hours to silver nitrate, and 

 mounted in dammar varnish without previous exposure to the light. 



Staining Tissues treated with Osmic Acid. — Damaschino, in a 

 communication | to the Societe de Biologic, advocates osmic acid in 

 the form of a solution of 1 per cent, for human sjnnal cord divided 

 into lengths of 1 cm., and for the spinal cord of smaller animals 

 treated entire ; he afterwards hardens in absolute alcohol. If it is 

 then not sufficiently hard, the preparation is saturated with gum before 

 being placed in the alcohol ; the sections, which are penetrated with 

 gum, are transferred unstained to Canada balsam without being pre- 

 viously freed of gum by means of water. 



Eeferring to this communication (which contains no really new 

 point), L. Malassez | remarks on the difficulty of staining substances 

 which have been treated with osmic acid, and for this reason he first 

 stains the sections with other staining matters, and then exposes them 

 to the action of osmic acid, and this in such a way as to allow only 

 the vapour of the solution of acid to act. He claims to have obtained 

 admirable results by this method, since in this way all the properties 

 of the osmic acid come into play without affecting the other staining 

 substances. 



E. Hertwig § placed the animals (Ctenophora) examined by him 

 in a • 05 per cent, solution of osmic acid, to which in some cases 

 he added acetic acid solution of 0* 2 per cent, for from 5 to 15 minutes, 

 according as he wished to investigate the epithelium or the elements 

 of the gelatinous tissue ; he then stained with camdne and finally 

 preserved in dilute glycerine. 



Mounting the "Saw" of the Tenthredinidae.H — Mr. P. Cameron 

 describes his method of mounting and preserving the " saw " of the 

 Tenthredinidae for microscopical examination, a method which can be 

 applied to microscopical mounting generally. 



* Arcl). per le Sci. Med., iv. (1S80) pp. 221-46 (1 pi.). Cf. Zool. Jahresber. 

 Neapel for 1880, i. p. 44. 



t Gazette medic. Add., li. (1880) p. 636. t H^id., p. 637. 



§ Jenaisch. Zeitscbr., xiv. (1880) p. 315. Cf. Zool. Jahresber. Neapcl for 

 1880, i. p. 41. 



II Trans. Entomol. Soc. Lond. 1881, pp. 576-7. 



