22 HISTOLOGICAL TECHNIC 



two days, when it is filtered. This fluid stains nuclei and connective 

 tissue red, cell protoplasm yellow. 



Staining in Bulk 



^[ By this is meant the staining of blocks of tissue before cutting 

 into sections. The method is much less used than formerly. It is 

 slower than section staining and more difiicult to control. Blocks of 

 the hardened tissue are transferred to the stain from water or alcohol 

 according to the solvent of the stain. Alum-carmine and borax- 

 carmine are the most used general bulk stains. 

 (i) Alum-carmine. 



Carmine, 0.5 to i gm. 



Ammonia alum, 4-per-cent. aqueous solution, loo c.c. 



After mixing the ingredients, the solution should be boiled fifteen 

 minutes, and after cooling, enough sterile water added to replace that 

 lost by evaporation. The time required for staining depends upon 

 the size of the specimen. There is, however, little danger of over- 

 staining. After washing out the excess of stain with water the speci- 

 men is dehydrated and embedded in the usual way. 

 (2) Borax-carmine, Alcoholic Solution. 



Carmine, 3 gm. 



Borax, 4 gm. 



Water, 93 c.c. 



After mixing the above, add 100 c.c. 70-per-cent alcohol, 

 allow the mixture to settle, then filter. 



About twenty-four hours is required to stain blocks 0.5 cm. in 

 diameter. Larger blocks require longer staining. 



Vm. Mountmg 



It is usually desirable to make permanent preparations or 

 "mounts" of the stained specimens. 



The most satisfactory media for mounting specimens are glycerin 

 and Canada balsam. 



(i) Glycerin. — Sections may be transferred to glycerin from 

 either water or alcohol. In the case of double-stained specimens — 

 haematoxylin-eosin — the glycerin should be tinged with eosin, as the 

 pure glycerin abstracts the eosin from the tissues. In many cases 

 satisfactory eosin staining may be obtained by simply placing the 



