NOTES AND MEMORANDA. 335 



cent, to the staining fluid, but it is advisable and in the 

 case of delicate tissues necessary to complete the hardening 

 process before staining. 



Staining. — Grenadier's alcoholic borax carmine is used. 

 Pure carmine, 2*5 per cent., is added to a solution of borax 

 4 per cent (in water), this is allowed to stand for two or three 

 days and occasionally stirred ; the greater part of the car- 

 mine will dissolve. To this solution is added an equal bulk of 

 alcohol of 70 per cent. This mixture must stand for a week 

 and then be filtered, when it is ready for use. If on keeping 

 more carmine is deposited it should be refiltered. 



The tissue is placed in this solution and allowed to remain 

 one, two, or three days according to its size ; it is hardly 

 possible to overstain, and there is sufficient alcohol in the 

 solution to prevent injury to any but the most delicate 

 tissues. For such tissues a solution can be prepared con- 

 taining more alcohol but of course less carmine. 



The tissue when removed from the staining fluid is placed 

 in alcohol of 70 per cent., acidulated with hydrochloric acid 

 (3 to 6 drops of the acid to 100 c.c. of spirit). This dissolves 

 out all excess of carmine and fixes the rest. The tissue a 

 dark purplish red when taken out of the borax carmine, 

 should be left in the acidulated alcohol till it acquires a 

 bright transparent look (3 to 6 hours), it may then be 

 transferred to absolute alcohol and afterwards to turpentine. 

 When thoroughly permeated with this latter (the time 

 necessary varying as the size of the lump of tissue) it is 

 ready for imbedding. 



Imbedding — This is done in paraffin and it is exceedingly 

 important to obtain a suitable paraffin. It should melt at 

 100° or 115° F. Paraffins of various melting points should 

 be kept in the laboratory ; they may be purchased at the 

 dealers. 



The tendency to curl up on the part of the section may be 

 reduced to a minimum by obtaining a paraffin of the proper 

 consistency, but this seems to vary according to the tem- 

 perature of the room in which the sections are cut. 



The paraffin must be melted in a small covered vessel in 

 a water oven, great care being taken to keep it in a dry 

 atmosphere. The temperature in the oven should never 

 rise more than two or three degrees above the melting point 

 of the paraffin used. 



When the paraffin is melted the tissue is removed from 

 the turpentine and placed in it, and this must be kept at its 

 melting point for some hours until the tissue is thoroughly 



VOL. XXII. NEW SER. Y 



