8 THE PKEPARATION OF MICROSCOPICAL OBJECTS. 



1. Ranvier's Alcohol : a mixture of one part of strong spirit 

 with two parts of water. The specimen should be put fresh into 

 the mixture and allowed to remain twenty-four hours or more. 



2. Miiller's Fluid: a solution of bichromate of potash with 

 a little sodic sulphate in water. 



D. Staining. 



Various re-agents are employed for the purpose of staining 

 preparations ; some of these merely colour the whole prepara- 

 tion more or less uniformly, but the most useful ones are those 

 which stain certain parts of the cells only, or at any rate stain 

 these much more strongly than the other parts. The most im- 

 portant are the following. 



1. Hsematoxylin. There are various preparations of hremato- 

 xylin, or logwood, used in microscopical work : the best is that 

 proposed by Kleinenberg and called by his name. It is pre- 

 pared thus : — 



(a) Make a satiu^ated solution of crystallised calcium chloride 



in 70 per cent, alcohol, and add alum to saturation. 



(b) Make a saturated solution of alum in 70 per cent, alcohol, 



and add (a) to (b) in the proportion of 1 to 8. 



(c) To the mixture of (a) and (b) add a few drops of a 



saturated solution of hsematoxylin in absolute alcohol. 

 The specimens, which must be perfectly free from all trace 

 of acid, should be left in the hsematoxylin in a covered vessel 

 or stoppered bottle for from one to twenty-four hours, according 

 to the size of the specimen and the depth of staining desired, 

 and then placed in strong spirit for some hours before mounting. 

 Heematox^'lin stains the nuclei of cells much more strongly than 

 the other parts. 



2. Borax-Carmine. This, which is perhaps the most generally 

 useful of all the stains in ordinary use, is prepared as follows. 

 Dissolve 2 parts of carmine and 4 parts of borax in 100 parts of 

 water : add an equal volume of 70 per cent, alcohol ; let the 

 mixture stand for a couple of days, and then filter. 



Specimens may be left in borax-carmine for from one to 

 twenty-four hours, or even for two or three days : on removal 

 they should be placed in acid-alcohol — i.e., 70 per cent, alcohol 

 to which a few drops of hydrochloric acid have been added — 

 until they become a bright scarlet colour, Avhen they shoidd he 



