STAINING FLUIDS. 25 



alcohol according to the usual method ; very deep staining is 

 therefore desirable. 



Green coloration of the nuclei. To effect this, Tafani em- 

 ploys a fluid containing three or four parts of a saturated 

 watery solution of aniline blue to some six or seven parts of a 

 saturated watery solution of picric acid. 



Eosine and Jicematoxylinfor staining bone. Busch recom- 

 mends eosine and hsematoxylin for double-staining the zone of 

 ossification in growing bone. The sections of decalcified bone 

 are first immersed a few days in a one-half per cent, chromic 

 acid solution, or in a one per cent, solution of the bichromate 

 of potassium, and then, after washing with water, in a watery 

 solution of eosine. In young bone, where ossification is pro- 

 gressing, the cartilage matrix is blue, while the nuclei of the 

 cartilage-cells adjoining the line of bone are red ; the contents 

 of the medullary spaces are also bright red, while in the bone 

 trabecles there is a combination of blue and red. 



Eosine for permanent specimens. Renaut has employed 

 eosine to differentiate all forms of protoplasm, whether bodies 

 or their processes. He either employs a watery solution alone, 

 or with the admixture of one-third its volume of alcohol. 

 The coloration is obtained after immersion of the sections from 

 one-half minute to one minute. They are then washed in 

 distilled water, and may be preserved in a neutral solution of 

 glycerine to which one per cent, of chloride of sodium has been 

 added to prevent the glycerine dissolving the eosine. These 

 preparations will then remain unchanged for months. 



In examining the fixed corpuscles of the subcutaneous tis- 

 sue, the same author injects beneath the skin a solution of 

 eosine and water (1-500), and then removes a portion of the in- 

 filtrated tissue with the scissors. The fibrous fascicles are un- 

 affected, while the elastic fibres take the color deeply. 



The fixed corpuscles appear as red granular plates, while 

 their nuclei take a very intense color. This reagent, therefore, 

 is well suited for the study of connective tissues. In special 

 instances the silver method may be used first, and then the 

 eosine. 



Preparation of tlie cornea. Klein has adopted the follow- 

 ing plan for exhibiting this most delicate tissue. He first burns 

 the centre of the cornea of a kitten with caustic potash, and 

 then, twenty-four hours later, brushes the surface with nitrate 



