1893.] MICROSCOPICAL JOURNAL. 79 



Nitrate of silver. — A solution is made in distilled water of 

 I grm. of silver nitrate to loo of water, and kept in a black 

 glass bottle. For use, one part of this is mixed with 3 parts of 

 distilled water. 



1. x\ membrane, the omentum for instance, has the solution 

 poured over it. When the tissue begins to get opalescent place 

 it in the sun, in a vessel of water. Mount in glycerin. . . . Do 

 not touch the membrane with the fingeres, and if it is soiled with 

 blood wash it very rapidly in distilled water. 



2. Extent! the membrane on the slide, let it dry till it adheres 

 to the edges of the glass, and pour on it the silver solution. 

 Expose to the sun, and wash in distilled water. . . . 



Nitrate of silver has the power to make out the contour of the 

 endothelial cells, by being reduced upon the intercellular cement. 

 Tn certain cases it is good to color cell nuclei. Wash, stain for 

 half an hour in alum carmine, wasli again, and mount in 

 glycerin or in balsam. 



Chloride of gold. — This is almost exclusively used for the 

 study of nerve endings. A one per cent, solution is kept in a 

 yellow bottle. . . . 



Summary. 



Fixation by alcohol. — A fragment of tissue the size of a 

 small hazel-nut is placed in 50 grammes of 90"^ alcohol for 24 

 hours. 



Hardening. — Place the tissue in water for 20 minutes. Trans- 

 fer to a solution of gum arabic for from 24 to 48 hours. Absorb 

 the mucilage from the surface by bibulous paper and place in 60 

 grms. of 90° alcohol for 48 hours. 



Sections. — Free-hand, or by Ranvier's or some other micro- 

 tome. Put the sections in water for 20 minutes. 



Staining. — Place the sections on a slide, stain with picro- 

 carmine. and mount, some in acidulated glycerin, others in glycerin 

 with a little picro-carmine 



Fixation by osmic acid. — A piece of tissue i mm. or more in 

 diameter is placed in i or 2 c. c. of osmic acid for from 12 to 

 24 hours. Wash in water for 12 hours. 



Hardening.— When taken from the water make free-hand 

 sections, or, if too soft, imbed in gum. 



Sections, — Free-hand or by microtome. The sections remain 

 in water for only a few minutes. 



Staining. — Transfer to a vessel full of alum carmine, i hour. 

 Wash in water for 5 minutes. 



Preservation. — Mount in water, which is to be replaced by 

 allowing glycerin to run under the cover. . . . 



Fixation by bichromate of ammonia. — A fragment of tissue 

 centimetre or i^ centimetres in diameter is placed in 100 grms. 

 of bichromate of ammonia. Leave it there for 10 days, often 

 renewing the solution. Wash for 24 hours in a large quantity of 

 water to which is added a crystal of tiiymol or of carbonic acid, 



