384 CHAPTER XXX. 



686. BETZ'S Methods (Arch. f. mik. Anat., 1873, p. 101). 

 Brain and spinal cord are first subjected to a preliminary 

 hardening, for some days or weeks, in 70 to 80 per cent, 

 alcohol containing enough iodine to give it a light brown 

 coloration. After this they are definitely hardened in 

 bichromate of potash of 3 per cent, for spinal cord, medulla 

 oblongata, and pons, 5 per cent, for cerebellum, and 4 per 

 cent, for cerebrum. 



For details see previous editions. 



687. 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 termina- 

 tion 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. 



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

 p. 254). Slices of fresh brain about one inch thick are 

 placed flat in a large vessel padded with cotton ; do not put 

 them one above the other. Cover them with the following 

 fluid (after cooling) : 



Miiller's fluid .... 3 parts. 



Methylated spirit .... 1 part. 



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., 



in which they remain for one week. Then change the 

 solution 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 



