144 Traoisactions of the Society. 



Hock from the spirit and most carefully remove the pins with the 

 forceps, sticking them into one side of the block ready for next use. 

 The head is then well washed in water, and transferred to the 

 following solutions, in the order and proportions named, allowing 

 it to remain at least three days in each : — 



(a) Glycerin, 1 part ; water, 3 parts. 



(b) Glycerin, 1 part ; water, 2 parts. 



(c) Glycerin, 1 part ; water, 1 part. 



(d) Glycerin, 2 parts ; water; 1 part. 



This is the final stage, and the head is mounted in the last (d) 

 solution to which should be added 3 minims of phenol to each 

 2 oz. of solution, wliicli will cause the whole to smell strongly of 

 carbolic. The solution should be filtered through filter-paper, and 

 be kept in a capped bottle. The glass tube which takes out the 

 solution should always be kept in the bottle, but should never 

 touch the bottom. This may be prevented by fitting the tube 

 tightly through a piece of card, which fits the neck of the 

 bottle. 



The mounting of a head is a matter of such vital imporcance 

 tliat I give a detailed description of it. The glycerin solution will 

 penetrate almost anything. It is necessary, therefore, to take 

 what may seem almost exaggerated precautions. 



Most of my slides are tM'enty-five year,3 old, and so far, most are 

 absolutely safe, though one or two do exude a very little at the 

 top in very hot weather. I lay the greatest stress upon the cement. 



It is composed of black sealing-wax dissolved in methylated 

 spirit, and marine glue. Mr. Enock used only this cement for 

 these mounts. 



The wax must be of the very best and be crushed in a mortar 

 until it becomes a fine powder. Methylated spirit is then added 

 and the mixing and grinding in the mortar continued until it is 

 sufficiently thin to filter through moderately fine muslin. When 

 filtered, an equal part of liquid marine glue is added and thoroughly 

 mixed in. If time is no object evaporation may be allowed until 

 the required consistency (about that of thin cream) is reached, 

 otherwise it must be reduced to that state by gentle heat. 



In building up cells I used vulcanite or ebonite rings, |-, |, and 

 f in. in diameter. Both sides of the rings should be rubbed on 

 sand-paper to remove the gloss, and the rings should be carefully 

 dusted before use, a cloth being passed through them. 



Mr. Enock used to fix, or secure, his heads in the cells, but 

 not so much latterly. 



I prefer them not fixed, as you can then place them in any 

 position. 



In fixing, Mr. Enock made use of two short lengths of fine 

 tubing, attached side by side, into which fitted two fine needles. 



