52 



that of a row and a half of cells ; but this must, of course, vary with the 

 special point it is required to elucidate. 



After the sections have been cut they may be preserved for any length 

 of time jin a mixture of spirit and water, until required for bleaching and 

 staining. 



In mounting the preparations when stained, two things must be con- 

 sidered, viz., the medium to be used, and the method of using it. 



The only medium I have found suitable for mounting sections, stained by 

 either of the methods I have described, is Canada balsam, hardened and dis- 

 solved in benzole. I have never yet been able to purchase any ready pre- 

 pared that I considered suitable, and have been compelled to make my own ; 

 the method which I employed, and found successful, is as follows: — 



About half a pound of ordinary Canada balsam is placed in a soup-plate, 

 and warmed gently for some weeks, being stirred two or three times daily. 

 I prepared mine on the top of the hot-water cistern of a bath-room, and 

 found this answer very well. As soon as when cool — not cold, — it can be 

 drawn out into tough threads, and does not stick to the fingers, it is to be 

 placed in a bottle, and covered with bsnzole. In a few days it will be dis- 

 solved, and is then to be filtered through filtering paper moistened with 

 benzole, when it will be ready for use. I find I get a far better preparation 

 by dissolving the balsam whilst tough than by continuing the drying until 

 it becomes hard and brittle, as recommended by some. If properly pre- 

 pared, it should be of a pale colour, and of about the consistency of oil of 

 cloves. 



The method of using it is as follows : — 



A glass slip is breathed on, and a clean cover placed instantly on the slip, 

 to which it adheres. A drop of two of the balsam, prepared as I have de- 

 scribed, is then placed on the cover. The object, which must be mounted 

 direct from the oil of cloves, has as much as possible of the oil drained off, 

 and is then placed in the balsam and covered with a few drops more of the 

 same medium, and the whole is pat away out of the dust for 12 hours or 

 longer. 



A fresh drop of balsam is now placed on the object, and the cover, with 

 the object and balsam on it, is turned over on to a clean slip. The latter is 

 then gently warmed, and the cover pressed down. 



In a few hours the superfluous balsam can be scraped off, and the slide 

 cleaned with a rag dipped in methylated spirit. If the balsam has been pre- 

 pared as I have described, there need be no fear of the cover being displaced 

 during this prooess. 



The slide can then be finished off with white zinc cement, or any other 

 that is preferred, and, when this is hard, can be labelled and put away in 

 the cabinet. 



The following objects were exhibited in the Library : — 



Ahyonclla fnngosa ... ... ... ... Mr. F. W. Andrew. 



Trans, sec. Sciatic Nerve ... ... ... Mr. M. J. Cole. 



Vert. sec. Mncous Membrane from Stomach) 

 of Dog ) 



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