170 COLLODION AND OTHEK IMBEDDING! METHODS. 



The syrup requires to be of a particular strength, viz. 

 double refined sugar, 2 ounces ; water, 1 fluid ounce. 



Wash the superfluous syrup from the surface, and put into 

 the ordinary mucilage for an hour or so before cutting. 

 Imbed in the freezing microtome with mucilage in the usual 

 way. Float the sections into water. 



309. Gum and Syrup Congelation Mass (COLE, Methods o/ 

 Microscopical Research, 1884, p. xxxix; Journ. Roy. Mic. 8oc. 

 (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. 



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

 Soc., 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 



