318 SUMMARY OP QUERENT RESEARCHES RELATING TO 



Gum and Syrup Preserving Fluid.* — The very great objection 

 to tlie use of freezing microtomes was tlie impossibility of taking 

 spirit-bardened material and cutting it without an eighteen or twenty- 

 four hours' preparation. Up to a few months ago, any one wishing to 

 cut by freezing had to take his specimens out of spirit, cut them of 

 convenient size, and soak them in water for twelve or more hours to get 

 rid of the spirit, then place them in gum solution some hours further. 

 This was a great drawback, and rendered it a necessity that the 

 operator must think over what he wished to cut, and prepare it 

 through twenty-four hours previously ! 



All this is changed. Specimens are now kept the year round, if 

 the operator chooses, in gum and syrup, having a little carbolic acid 

 in it, and he freezes and cuts any tissue so placed at any moment he 

 likes. 



To make the gum and syrup medium, take of gum mucilage f (B.P.) 

 five parts ; syrup, % three parts. Add five grains of pure carbolic acid 

 to each ounce of the above medium. 



Tissue may remain in this any length of time. For brain, spinal 

 cord, retina, and all tissues liable to come in pieces, put four parts of 

 syrup to five of gum. 



The operator will do well to make the gum mucilage and syrup 

 separately, and to keep them so till wanted. 



Cutting Tissues Soaked in Gum and Syrup Medium. §— Take a 

 piece of tissue not more than an eighth of an inch thick, and press it 

 gently between a soft cloth to remove all the gum and syrup from the 

 outside of the tissue. Set the spray going, and paint on the freezing- 

 plate a little gum mucilage : then put the tissue upon this and surround 

 it with gum mucilage with a camel-hair bi'ush. The tissue is thus 

 saturated with gum and syrup, but surrounded when being frozen 

 with gum mucilage only. This combination prevents the sections 

 curling up, on the one hand, or splintering from being too hard 

 frozen on the other. Should freezing have been carried too far, the 

 operator must wait a few seconds. It ought to cut like cheese. 



Gum Styrax as a Medium for Mounting Diatoms. |1 — Keferring 

 to Dr. Van Heurck's recommendation of "styrax,"^ Mr. F. Kitton 

 writes that the resin which is the product of Liquidambar orientale is 

 prescribed in the British Pharmacopoeia under the name of gum 

 styrax, and in the drug trade is known as " strained gum styrax." It 

 has the colour of the old-fashioned black treacle, but is of greater 

 consistency ; a temperature of 212° renders it fluid. In its com- 

 mercial state it is unfit for microscopic purposes, first from its 



* Cole'a ' Methods of Microscopical Kesearch,' 1884, p. xxxix. 



t Gum mucilage B.P. is made by placing 4 oz. of picked gum acacia in 

 6 oz. of distilled water and stirring occasionally until the gum is dissolved. 

 This is to be strained through muslin. 



X Syrup is made by dissolving 1 pound of loaf sugar in 1 pint of distilled 

 water and boiling. 



§ Cole's ' Methods of Microscopical Eesearch,' 1884, pp. xxxix.-xl. 



II Sci.-Gossip, 1884, p. 66. 



H See this Journal, iii. (1883) p. 741. 



