100 rilU'TKK VIII. 



india-rubl)er in very small pieces, dissolved by heating to 100 C. for 

 twenty-four hours, or several days to 60 C. Clear with xylol. For 

 very brittle objects. 



153. Soap Masses. These have never been much used, and are now 

 entirely discarded. But see early editions, or POLZAM (Morph. Jahrb., 

 iii, 1877, p. 558); KADYI (Zool. Anz., 1879, vol. ii, p. 477); DOLLKEN 

 / ''. iviss. Mik., xiv, 1897, p. 32). 



Gelatin Masses. 



154. Gelatin Imbedding is a method that has the ad- 

 vantage of being applicable to tissues that have not been 

 in the least degree dehydrated. 



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

 fusion masses, with the difference that the objects are pre- 

 pared by saturation with water instead of alcohol or a 

 clearing agent. After the cooling of the mass it may some- 

 times 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 formaldehyde 

 (NICOLAS), or it may be frozen (SOLLAS). 



The mass can be removed from the sections by means of 

 warm water. 



155. Glycerin Gelatins, KLEBS' (Arch. mik. Anat., v, 1869, p. 165). 

 A concentrated solution of isinglass mixed with half its volume of 

 glycerin. 



KAISER'S (Bot. Centralb., i, 1880, p. 25). One part by weight of 

 gelatin is left for about two hours in 6 parts by weight of water ; 7 parts 

 of glycerin are added, and for every 100 grin, of the mixture 1 grin, of 

 concentrated carbolic acid. The whole is warmed for ten to fifteen 

 minutes, stirring all the while, until the whole of the flakes produced by 

 the carbolic acid have disappeared. 



.GERLACH's (Unters. a. d. Anat. Imt. Erlar)gen,~\.884<; Journ. Roy. Mic. 

 Soc., 1885, p. 541). Take gelatin, 40 gnn. ; saturated solution of arsenious 

 acid, 200 c.c. ; glycerin, 120 c.c. Clarify with white of egg. The objects 

 to l>e prepared for imbedding by a bath of one third glycerin. 



APATHY (Mitth. Z. Stat. Neapel, xii, 1897, p. 718, and Zeit. wiss. 

 Mikr., xxix, 1913, p. 472) soaks small objects first in glycerin and water 

 (equal parts) and then for at least 24 hours at 40 C. in a solution of 

 1 part of gelatin in 3 of glycerin and 6 of water. They are then 

 arranged in some of this in an imbedding box, and the whole is warmed 

 (over calcium chloride) in a stove at 45 to 60 C. until the mass has 

 evaporated down to one half, losing 5 of its 6 volumes of water (as I 



