92 MICROSCOPICAL TECHNIQUE. 



should be changed once or twice, or until the formalin solution 

 no longer gives a dirty, brownish-red colour. Care must be taken 

 to bring all portions of the object into contact with the solution, 

 and the object must be given the shape which it is to retain per- 

 manently, since the formalin solution causes it to assume a 

 consistency such that its shape cannot afterwards be modified. 

 In the formalin solution the organs change colour and become of 

 a dirty, bluish-grey. On now placing them in 95 per cent, alcohol 

 the normal colour returns. Before permanently placing the organ 

 in alcohol it must be washed with alcohol until the latter no 

 longer becomes cloudy. The material must not be washed with 

 water. The material is left in alcohol for a varying time until 

 the normal colour has again fully returned ; if left longer the 

 alcohol removes the colour. For a kidney or spleen twenty-four 

 hours is sufficient. The permanent preserving fluid is equal 

 parts of glycerine and water; the material floats at first, but 

 sinks later ; the colour is now at its best ; after a little time the 

 fluid becomes yellowish and requires renewal. Tissues so pre- 

 served have not undergone the slightest alterations in colour 

 during nine months. The method is not applicable to the 

 preservation of any other colour than that of blood — thus, 

 icteric liver is not well shown. — British Medical Journal^ June 

 20th, 1896 ; Epit., p. 100. 



Glycerine Jelly, made by Gage's formula, is said to be clear 

 and bright : — Let gelatine, 25 gm., stand in enough distilled water 

 to cover it until softened, then pour off" excess of water, and heat 

 gelatine till dissolved. {Mem., As the quantity of water taken up 

 varies with the time, it is usually better to add four times the 

 weight of the gelatine taken.) Next add white of egg, 5 c.c, to 

 the melted gelatine, stir thoroughly, and heat till the albumin 

 coagulates. Filter while hot ; then add chloral hydrate, 5 gm., 

 and as much glycerine as the gelatine solution measures. Again 

 heat gently and filter. The jelly is then ready for use. — Phar- 

 maceutical Journal. 



