NEUROLOGICAL METHODS. 387 



Brains may be kept for months in the mixture (ibid., 1896, 

 p. 568). 



GKROTA (Zeit. f. wiss. Mik., xiii, 1896, p. 314) puts human 

 brains into a 5 to 10 per cent, solution of formol, and after 

 twenty-four hours removes the pia and changes the liquid ; 

 this is also further done every five to seven days, and in one 

 or two weeks the hardening is complete. In the case of 

 foetal brains of Ganix, Fells, and Homo, he first injects the 

 vascular system with a 10 to 15 per cent, solution of formol 

 in 85 per cent, alcohol, and then brings the heads into the 

 5 to 10 per cent, watery solution ; after one or two days he 

 removes the brains from the skulls and puts them back for 

 fifteen to twenty days into the formol. 



MABINA (Riv. Pat. Nerv. Ment., Firenze, ii, 1897, p. 20 ; Neur. Centralb., 

 xvi, 1897, p. 166; Zeit. f. iviss. Mik., xiv, p. 231) fixes portions of central 

 nervous system for four to eight days in a freshly prepared mixture of 100 c.c. 

 90 per cent, alcohol, 5 c.c. formol, and O'l grm. chromic acid, changing the 

 mixture daily. 



OKTH (Berl. kll/n. Wochenschr., 1896, No. 13; Zeit. f. wiss. 

 Mik., xiii, 3, 1896, p. 316) recommends under the title of 

 Formol-Muller (or, abbreviated, F. M.), a mixture of one part 

 of formol to ten of liquid of Miiller ( 57). It must be 

 freshly prepared, and changed every few days. Small pieces 

 of tissue may be sufficiently hardened in a few hours in a stove. 



KEAUSS (Trans. Amer. Mic. Soc., xvii, 1896, p. 315; Zeit. 

 f. wiss. Mik., xiii, 1896, p. 493) finds that formalin in different 

 strengths hardens well, but causes a notable shrinkage of 

 neuroglia, and prefers liquid of Miiller. 



See also SIEMKRLING, NeuroL Centralb., xviii, 1899, p. 472 ; 

 Zeit. f. wiss. Mik., xvi, 4, 1900, p. 470 (10 per cent, formol 

 gives a good consistency ; but if it is allowed to act long, 

 stains will be bad unless the material is after-hardened for 

 some weeks in solution of Miiller, and the sections mor- 

 danted [for myelin stains] with 0'5 per cent, chromic acid). 



For special mixtures for GOLGI impregnations see 752. 



693. Nervous Centres of Reptiles, Fishes, and Amphibia. 

 MASON (Central Nervous System of Certain Reptiles, etc.; WHITMAN'S 

 Methods, p. 196) recommends iodised alcohol, six to twelve hours; 3 per 

 cent, bichromate, with a piece of camphor in the bottle, and to be changed 

 once a fortnight until the hardening is sufficient (six to ten weeks). 



BUKCKHARDT (Das Centralnervensystem von Protopterus, Berlin, 1892 ; 



