BRAIN. 323 



solution of chromic acid for a fortnight, and then in rectified 

 spirit. 



665. Cerebrum (BEVAN LEWIS, The Human Brain, p. 102). 

 Methylated spirit, twenty-four hours in a cool place. Miiller's 

 solution, three days in a cool place. Then change the liquid ; 

 and after three days more change it again, or, preferably, 

 substitute a 2 per cent, solution of potassium bichromate. At 

 the end of the second week a solution of double the strength 

 may be added ; and if, at the termination of the third week, 

 the mass is still pliable and of the consistence of ordinary 

 rubber, it is as yet unfit for section cutting, and the reagent 

 should be replaced by a solution of chromic acid. 



666. Brain (HAMILTON, Journ. of Anat. and Physiol., 1878, 

 p. 254). Take a fresh brain and make a series of incisions 

 into different parts, still keeping everything in situ ; or slice 

 it into any number of segments about one inch thick, but of 

 the whole length or breadth of the organ, as may be desired. 

 Do not remove the membranes ; they form a projection for the 

 superficial layers, and do not interfere with the hardening 

 process. The large segments are placed flat in a large vessel 

 padded with cotton ; do not put them one above the other. 

 Cover them with the following fluid : 



Miiller's fluid ... 3 parts. 



Methylated spirit . . 1 part. 



(Heat is evolved on mixing these liquids, and the mixture 

 must be allowed to cool before pouring it over the brain 

 tissue.) Put the preparations away in an ice-safe. Turn the 

 segments over next day. Change the solution in a fortnight 

 or three weeks; or if on examining a section of one of the 

 pieces it is found that the hardening reagent has penetrated 

 to the interior, they may be at once removed to the following 

 mixture : 



Bichromate of ammonia . . 1 grm. 



Water . . . . 400 c.c. 



111 wliic'li they remain for one week. Then change the solu- 

 tion to one of 1 per cent, for one week ; and let this be followed 

 by a solution of 2 per cent, for another week, or longer if 

 required. The pieces will now be sufficiently hard for cutting ; 

 they may be kept permanently in solution of chloral hydrate, 

 twelve grains to the ounce. 



