388 CENTRAL NERVOUS SYSTEM. 



733. Spinal Cord (KRAUSE, Arch.f. mik. Anat., 1875, p. 226). 

 Solution of Mull er, twenty-four hours. Then chromic acid, 

 1 per cent. On the fourth day the solution must be changed 

 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. 



CIAGLINSKI (Zeit.f. wiss. Mik., viii, 1, 1891, p. 19) recom- 

 mends hardening for three or four months in solution of 

 Miiller, renewed every day during the first week, and after- 

 wards as often as it becomes turbid. Liquid of Erlicki 

 will harden in as many weeks, but has the defect that if 

 preparations are left longer in it they are injured by the 

 formation of the above-mentioned precipitates (last section 

 and 77). 



734. Encephalon (M DUVAI/S methods, EOBIN'B Journal de 

 I'Anatomie, 1876, 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 Miiller'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 extracted before cutting, as the cranium will be found to be com- 

 pletely decalcified.) 



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. 



