378 NERVES. 



not to add too much). Twenty-four hours in the bath is 

 enough, but preparations may stay in it longer (in one case 

 as much as two months) without hurt, provided they be kept 

 in the dark. Wash, treat with alcohol for a quarter of an 

 hour, then for the same time with absolute alcohol, and the 

 same time with celloidin solution, after which they are 

 hardened for about the same time in 70 per cent, alcohol, cut 

 and mounted as usual. 



718. SALA (Zeit. f. wiss. ZooL, lii, 1, 1891, p. 18 ; Zeit. f. 

 wiss. Mik., viii, 3, p. 389), in a paper written in Golgi's labora- 

 tory, gives the rapid process as follows (for the pes hippocampi 

 ma/joris of small mammals) : Four to five days in 2 per cent, 

 bichromate of potash ; twenty- four to thirty hours in a bichro- 

 mate and osmium mixture containing 8 parts of the bichro- 

 mate solution to 2 of the osmium solution ; and a silver-bath 

 of 0*75 per cent, strength. He finds Greppin's hydrobromic 

 acid variation not merely useless, but hurtful. And he 

 thinks that Sehrwald's process for imbedding the material in 

 paraffin with the object of getting very thin sections is a 

 mistake. The chief quality of Golgi's process is that it 

 admits of the following of nerve-cell processes for a very great 

 distance. Evidently this cannot be done with very thin sec- 

 tions. It is better simply to wash the preparations taken from 

 the silver-bath with water, fix them to a cork with gum, put 

 the whole into alcohol for a few hours to harden the gum, 

 and cut with a microtome without imbedding. 



Other Nerve Methods. 



719. Structure of Medullated Nerve. In order to demonstrate 

 the axis-cylinder and the sheath of Schwann, the myelin may 

 be removed. This may be done by boiling in caustic soda, 

 and then neutralising ; by boiling in a mixture of absolute 

 alcohol and ether, and adding caustic soda; by boiling in 

 glacial acetic acid ; by boiling in fuming nitric acid, and 

 adding caustic potash ; or by treating with eau de Javelle. 



720. Neuroceratin Structures (&ALLI, Zeit.f. wiss. Mik., iii, 1, 1886, 

 p. 467). An ischiatic nerve is excised, and fixed and hardened for eighteen 

 to twenty minutes in solution of Miiller. Small portions of the nerve are 

 then further treated for one or two days with solution of Miiller diluted with 

 2 parts of water, then for a quarter of an hour with glycerin containing 1 or 



