156 TMBKDDING METHODS. 



solidify for hours, or, indeed, not at all. The more soap you have in your 

 alcoholic solution the more water must you add in order to get a transparent 

 mass, and the more may you add without depriving the solution of the 

 faculty of solidifying. Besides the mass prepared in the proportions given 

 above, useful masses may be made for certain purposes with 10, 20, 30, 40 

 per cent., or more or less of soap in alcohol. Weisker has employed a mass 

 composed of about equal parts by weight of soap and alcohol. Such a mass 

 is transparent, but yellow and oily, and takes a long time to solidify. When 

 cool it is very tough. It requires a considerable temperature to liquefy it, 

 and has less penetrating power than the more alcoholic masses. It is, 

 however, very suitable for hard, and especially for chitinous, structures. 



The mass recommended above boils at about 60 to 70 C, 

 Objects should be imbedded in it in a watch-glass or in paper 

 cases in the usual way. Whilst cutting, wet the knife and 

 the mass with strong alcohol (one advantage of this method 

 is that the knife remains perfectly clean). The sections are 

 brought into 96 per cent, alcohol, which frees them from the 

 mass instantaneously if warmed, and after a time if left cold. 



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

 123 ; PFITZEB, Ber. deutsch. bot. Ges., 1887, p. Ixv ; Journ. Roy. Mic. 

 Soc., 1888, p. 316). 



Gelatin Masses. 



286. 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. 



287. 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. 



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



I 



