1893.] MICROSCOriCAL .lol'KNAI.. 79 



Nitrate of silver. — A solution is madf in (iistillcii water of 

 I gnn. (jf silver nitrate to icx) of water, and kept in a black 

 f^Iass bottle. For use, one part of this is mixed with 3 parts of 

 distilled water. 



1. A membrane, the omentum for instance, has the solution 

 poured over it. When the tissue begins to <^et oj)alescent place 

 it in tiie sun, in a vessel of water. Mount in <^lycerin. . . Do 

 not touch the membrane with the fin^eres, and if it is soiled with 

 blood wash it very rapidly in distilled water. 



2. Extend the membrane on tiic slide, let it dry till it adheres 

 to the edfjes 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 reducetl upon the intercellular cement. 

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

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

 glvcerin 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. . . . 



SUMM.\K\ . 



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 arable for from 24 to 4S 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 glvcerin. others in glycerin 

 with a little picro-carniine 



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 tor only a few minutes. 



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

 Wash in water for ^ minutes. 



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

 allowing gbcerin to run under the co\er. . . . 



Fixation by bichromate of ammonia. — A tragment 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 crvstal of tli\niolorof carlionic acid. 



