208 COLLODION AND OTHER IMBEDDING METHODS. 



317. 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, retinae, and all 

 tissues liable to come in pieces put 4 parts of syrup to 5 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 6 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. They may remain in it for " any length of time, 

 all the year round " if desired. 



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. 

 The mass ought to cut like cheese. Should freezing have 

 been carried too far, wait for a few seconds. 



318. Dextrin Congelation Mass (WEBB, The Microscope, ix, 

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

 solution of dextrin in solution of carbolic acid in water 

 (Iin40). Use heat for making the solution if desired. This 

 medium is much cheaper than the gum and syrup mass, and, 

 according to Webb, possesses superior cutting qualities. 



319. Gelatin Congelation Mass (SOLLAS, Quart. Journ. Mic. 

 S'oc., xxiv, 1884, pp. 163, 164; Journ. Roy. Mic. Soc. [N.S.], 

 iv, 1884, p. 316). "Instead of gum one uses gelatin jelly. 

 This is prepared and clarified in the usual manner. It should 



set into a stiff mass when cold The tissue to be cut is 



transferred from water to the melted jelly, and should remain 

 in it till well permeated." 



The sections are transferred to a slide as soon as cut. On 

 touching the glass they adhere to it. When enough sections 

 have been thus arranged they are covered with a drop of 



