STAIN TOR NETJROCERATIN FUNNELS. 313 



2 per cent, solution of bichromate of potash 10 parts. - 



1 per cent, solution of osmic acid . . .2 parts. 



After about an hour's immersion the piece of nerve may 

 be cut into lengths of to 1 cm., which are put back into the 

 liquid. 



Four hours after the first immersion of the nerve in the 

 mixture, begin to put the pieces into nitrate of silver solu- 

 tion, transferring a certain number of pieces every three 

 hours, so as to be sure that some of them shall have had a bi- 

 chromate bath of a proper duration. (This duration may, 

 roughly speaking, be said to lie between six and twenty-four 

 hours.) 



The strength of the nitrate of silver solution is O50 per 

 cent. The duration of the silver-bath must not be less than 

 eight hours ; it may be indefinitely protracted. 



Dehydrate, clear with turpentine, mount in dammar. 



The method is more expeditious and easier of application 

 than the bichromate and silver-nitrate method, and the results 

 are somewhat more precise, but the preparations do not keep 

 in dammar. 



These two methods serve for the demonstration in peripheral 

 medullated nerve-fibres of the funnel-shaped coils of sustain- 

 ing filaments discovered by Rezzonico in the medullated 

 fibres of the spinal cord. 



In all methods for the demonstration of the funnels it is 

 important to observe the utmost delicacy of manipulation, 

 and in particular, the fibres must not be stretched; their stretch- 

 ing is a weak point in the methods of Ranvier (No. 656). 



MONDINO (Arch, per le Sci. Med., viii, p. 45 ; Zeit. f. wiss. 

 Mik., 1885, p. 547) recommends that the preparations be left 

 in the bichromate mixture longer than directed by Golgi 

 viz. from one to eight days ; and also that they be left for 

 over twenty-four hours in the silver-bath. 



For some minutiae concerning the application of the bichromate and silver 

 nu-thod to cerebro-spinal nerves, see PETRONE, in Internat. Monatschr. /. 

 Anat., v, 1, 1888, or Zeit.f. wiss. Mik., v, 2, 1888, p. 238. 



653. Stain for Neuroceratin Funnels ((>ALLI, Zeit.f. wiss. Mik., iii, 

 1, 1886, p. 467). An ischiatic nerve is excised, and fixed and hardened for 

 right eon to twenty days in solution of Miiller. Small portions of the nerve 

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

 with two parts of water, then for a quarter of an hour with glycerin con- 



