322 CENTRAL NERVOUS SYSTEM. 



for fresh. A few days later (when the cord appears hard), 

 the chromic acid is removed by means of water, and the cord 

 put into spirit, followed by absolute alcohol, which must be 

 changed at least twice. 



663. Encephalon (M. DUVAI/S methods, ROBIN'S Journal de 

 I'Anatomie, 187.6, p. 497). First Method. Place the fresh 

 tissues in solution of bichromate of potash 25, water 1000, 

 change the liquid after the first twenty-four hours, and again 

 after three or four days. After two or three weeks place the 

 preparations in chromic acid of 3 per 1000, change the liquid 

 every day for the first week, and after that every eight days 

 until the middle of the second month, after which time it is 

 no longer needful to change the liquid. The preparations 

 must remain at least two months in the chromic acid; the 

 longer they remain in it the better. A few fragments of cam- 

 phor should be added to the liquid in order to prevent the 

 growth of mould. 



Second Method. Place the fresh tissues in a mixture of equal parts of 

 glycerin and acetic acid ; after twenty-four hours remove them to Muller's 

 solution, and after forty-eight hours more to chromic acid. (The strength 

 of the solution is not indicated.) Change the chromic acid once or twice, 

 and the preparations will be fit for cutting in about eight or ten days. (Small 

 encephala (rat, bat) need not be extracted from the cranium provided this be 

 largely opened before immersing them in the glycerin, nor need they be ex- 

 tracted before cutting, as the cranium will be found to be completely decal- 

 cified.) 



This method is highly expeditious, and furnishes hardened tissues of a 

 singularly homogeneous consistence, quite without fragility, but it should 

 only be employed for the purpose of obtaining general views of structural 

 relations, as the anatomical elements are somewhat changed by it: cells and 

 axis-cylinders swell. 



664. Cerebrum (RUTHERFORD ; from SEVAN LEWIS). L'lace 

 small portions of cerebrum in methylated spirit for twenty-four 

 hours, in a cool place. After that, put them into the following 

 solution : 



Chromic acid . . 1 part. 



Bichromate of potash . . 2 parts. 



Water . . 1200 



Change the liquid at the end of eighteen hours, and then 

 once a week. Should the tissue not be sufficiently tough for 

 cutting at tin- end of six weeks, phirr it in ;i ,'fli per cent. 



