138 CHAPTER IX. 



tearing of delicate elements, and it is better to infiltrate the 

 tissues with a mass that does not crystallise in the freezing 

 mixture, but becomes hard and tough. HAMILTON (Journ. 

 of Anat. and Phys., xii, 1878, p. 254) soaked tissues in 

 syrup of a particular strength, viz. double refined sugar, 2 

 ounces ; water, 1 fluid ounce ; then washed the superfluous 

 syrup from the surface, and put into ordinary gum mucilage 

 for an hour or so, and then imbedded in the freezing micro- 

 tome with mucilage in the usual way. 



178. Gum and Syrup Congelation Mass (COLE, Methods of 

 Microscopical Research, 1884, p. xxxix ; Journ. Roy. Mic. Soc. 

 [N.S.], iv, 1884, p. 318). Gum mucilage (B.P.), 5 parts; 

 syrup, 3 parts. (For brain and spinal cord, retina, and all 

 tissues liable to come in pieces put 4 parts of syrup to five 

 of gum). Add 5 grains of pure carbolic acid to each ounce 

 of the medium. 



(Gum mucilage [B.P.] is made by dissolving 4 ounces of 

 picked gum acacia in G ounces of water. 



The syrup is made by dissolving 1 pound of loaf sugar in 

 1 pint of water and boiling.) 



This medium is employed for soaking tissues previous to 

 freezing. 



The freezing is conducted as follows : The gum and syrup 

 is removed from the outside of the object by means of a cloth ; 

 the spray is set going and a little gum mucilage painted on 

 the freezing plate ; the object is placed on this and surrounded 

 with gum mucilage ; it is thus saturated with gum and syrup, 

 but surrounded when being frozen with mucilage only. This 

 combination prevents the sections from curling up on the 

 one hand, or splintering from being too hard frozen on the 

 other. Should freezing have been carried too far, wait for 

 a few seconds. 



179. Dextrin Cong-elation Mass (WEBB, Tie Microscope, ix, 

 1890, p. 344; Journ. Roy. Mic. Soc., 1890, p. 113). Thick 

 solution of dextrin in solution of carbolic acid in water 

 (1 in 40). 



180. Gelatin (SoLLAS, Quart. Journ. Mic. Soc., xxiv, 1884, pp. 1(53, 

 164; Journ. Roy. Mic. Soc. [N.S.], iv, 1884, p. 316). Gum Gelatin 

 (.JACOBS, Amer. Natural., 1885, p. 734; Journ. Roy. Mic. Soc., 1885, 



