383 DR. PRITCHARO. 



twenty-four to twenty-eight hours. By that tune the alcohol 

 will have extracted the Avater from the mucilage, leaving 

 behind the gum in the form of a tough mass. 



This method is recommended for other tissues by Strieker. 



It is not necessary to use absolute alcohol; methylated 

 spirit of the commercial strength answers as well, if not 

 better ; and should the cochlea, on picking away the sur- 

 rounding gum, be found not sufficiently hard, it may be placed 

 in absolute alcohol for a few minutes. 



The cochlea thus prepared may be cut by means of Stir- 

 ling's machine and a sharp razor, care being taken to float 

 the sections in rectified spirit, in order that the supporting 

 gum may not be dissolved. 



I found the following composition, Avhich is recommended 

 by Dr. Ferrier, very useful for holding the tissue in the 

 machine : 



Lard 1 part. 

 Spermaceti 2 parts. 

 Parafiin 5 parts. 

 Melt over a water bath. 



Before leaving the subject of cutting the sections I must 

 call attention to a very important point, namely, that of the 

 sharpness of the razor. It is simply impossible to get satis- 

 factory sections without a very sharp razor ; to keep it sharp 

 it should be stropped after making every dozen sections, and 

 great care must be taken that the edge is not injured by 

 cutting against anything hard, or else it Avill have to be re- 

 grovmd. I found, with a little practice and care, that I could 

 manage to keep a good razor sharper than is usually sent out 

 from the cutler's as ground and set. 



Staining the sectio?is. — Of course many sections should be 

 put up unstained ; but it is better to have some stained, and 

 if they are to be mounted in Canada balsam or gum dammar 

 some such process becomes necessary. 



I have succeeded in obtaining very good results with two 

 staining agents, viz. carmine and gold. 



1st. Carmine staining. For this purpose Beale's carmine 

 fluid, diluted eight times with water, is by far the best to 

 use ; the sections should only be allowed to remain in it 

 from six to twelve hours, or twenty-four if all the tissues 

 are to be highly coloured, and then they should be removed 

 and washed in water. 



I may mention, by the way, that this plan answers un- 

 commonly well for staining all tissues Avhich have been 

 hardened in chromic acid. 



