COLLODION AND OTHER IMBEDDING METHODS. 135 



celloidin-paraffin solution. The mass is hardened by throwing it into a 

 saturated solution of paraffin in chloroform or in toluene, and is finally 

 imbedded in pure paraffin in the usual way. 



See also the modifications of DAHLGEEN, Journ. Applied Microsc., 1898,. 

 p. ^7 (Journ. Roy. Mic. Soc., 1898, p. 489) ; SABUSSOW, Mitth. Zool Stat. 

 Neapel, xii, 1896, p. 353 ; MITEOPHANOW, Arch. Zool. Exper. [3], 3, 1896,. 

 p. 617). 



Other Cold Masses. 



167. Joliet's Gum and Glycerin Method (Arch. Zool. Exper. 

 et Gen., x, 1882, p. xliii ; Journ. Roy. Mic. Soc. [N.S.], ii r 

 1882, p. 890). Pure gum arable dissolved in water to the 

 consistency of a thick syrup. (Solutions of gum sold under 

 the name of strong white liquid glue [" colle forte blanche 

 liquids a froid "] may also be used ; they have the advantage 

 of having a uniform consistency.*) Pour a little of the 

 solution into a watch glass, so as not quite to fill it, add 

 from 6 to 10 drops of pure glycerin, stir until thoroughly 

 mixed. In the winter or in rainy weather less glycerin 

 should be taken than in the summer or dry weather. 



The object is imbedded in the mass in the watch glass, 

 and the whole left to dry for from one to four days. When 

 it has assumed a cartilaginous consistency, a block contain- 

 ing the object is cut out, turned over, and allowed to dry 

 again until wanted for use. A stove, or the sun, may be 

 employed for drying, but it is best to dry slowly at the 

 normal temperature. 



This process may render service occasionally in the study 

 of extremely watery organisms, such as Salpa, or the Cteno- 

 phora. 



168. STEICKEE'S Gum Method (Hdb. d. Gewebel., p. xxiv). A concen- 

 trated solution of gum arabic. The object is imbedded in the gum in a 

 paper case. The whole is thrown into alcohol, and after two or three days 

 may be cut. The alcohol should be of about 80 per cent. (MATES). 



I have seen masses of sufficiently good consistency prepared by this simple 

 method. 



169. ROBEBTSON'S Grape-sugar Method, see Journ. of Anat. and, 

 Physiol., xxiv, 1890, p. 230; Zeit.f. wiss. Mik., vii, 1, 1890, p. 33. 



* It is highly probable that these commercial preparations contain gelatin, 

 and perhaps some other gum besides gum arabic. 



