GELATIN MASSES. 191 



the mass instantaneously if warmed, and after a time if left 

 cold. 



291. Other Soap Masses (FLEMMING, Arch. f. mik. Anat., 1873, p. 

 123 ; PFITZEE, Her. deutsch. bot. Ges., 1887, p. Ixv ; Journ. Boy. Mic. Soc., 

 1888, p. 316 ; POLI, Journ. de Micr., xiii, 1889, p. 337 ; Journ, Roy. Mic. 

 Soc., 1889, p. 835). 90 per cent. ; alcohol, 1 part ; glycerin, 1 part ; glycerin 

 soap, 1 to 2 parts. Heat the glycerin and spirit on a water-bath to 60 or 

 70 C., and drop the soap into it in small pieces. 



Gelatin Masses. 



292. Gelatin Imbedding is a method that has the advantage 

 of being applicable to tissues that have not been in the least 

 degree dehydrated, and may render great service in the study 

 of very watery objects. 



The modus^operandi is, on the whole, the same as for other 

 fusion masses, with the difference that the objects are prepared 

 by penetration with water instead of alcohol or a clearing 

 agent. After the cooling of the mass it may sometimes be 

 cut at once, but it is generally necessary to harden it. This 

 may be done by treatment for a few minutes with absolute 

 alcohol (KAISER), or for a few days with 90 per cent, alcohol 

 (KLEBS) or chromic acid (KLEBS), or it may be frozen 



(SOLLAS). 



The mass is removed from the sections by means of warm 

 water. 



293. Klebs' Gelatin (Glycerin Jelly) (Arch. f. mik. Anat., v, 

 1869, p. 165). A concentrated solution of isinglass is mixed 

 with half its volume of glycerin. 



294. Kaiser's Gelatin (Bot. Centralb., i, 1880, p. 25; Journ. 

 Roy. Mic. Soc., iii, 1880, p. 504). One part by weight of the 

 finest French gelatin is left for about two hours in 6 parts by 

 weight of water; 7 parts of glycerin are added, and for 

 every 100 grms. of the mixture 1 grm. of concentrated carbolic 

 acid. The whole is warmed for ten to fifteen minutes, stir- 

 ring all the while, until the whole of the flakes produced by 

 the carbolic acid have disappeared. Filter whilst warm 

 through the finest spun glass which has been previously washed 

 in water and laid whilst wet in the filter. 



295. Gerlach's Gelatin (GERLACH, Unters. a. d. Anat. Inst. 

 Erlangen, 1884; Journ. Roy. Mic. Soc., 1885, p. 541). Take 



