SUMMKES' ETHER METHOD. 179 



Methods for Watery Sections. 



322. Fol's Gelatin (FoL, Lehrb., p. 132). Four grammes of 

 gelatin are dissolved in 20 c.c. of glacial acetic acid by heating 

 on a water-bath and agitation. To 5 c.c. of the solution add 

 70 c.c. of 70 per cent, alcohol and 1 to 2 c.c. of 5 per cent, 

 aqueous solution of chrome alum. Pour the mixture on to 

 the slide and allow it to dry. In a few hours the gelatin 

 passes into the insoluble state. It retains, however, the 

 property of swelling and becoming somewhat sticky in pre- 

 sence of water. The slide may then be immersed in water 

 containing the sections, these can be slid into their places, 

 and the whole lifted out ; the sections will be found to be fixed 

 in their places. 



This method is especially useful for sections made under 

 water, large celloidiu sections amongst others. 



323. Poll (MALPIGHIA, ii, 1888, 2, 3; Zeit. f. wiss. Mik., v, 3, 

 1888, p. 361) arranges sections on a layer of melted Kaiser's 

 gelatin (supra, 288), adds glycerin, and covers. 



324. Prenzel and Threlfall's Gutta-percha (or Caoutchouc) 

 Method (Zool. Am., 1883, pp. 51, 301, and 423). This extremely elegant 

 method is not perfectly safe, the gutta-percha film being liable to tear ; and 

 is now, I believe, very generally abandoned. 



Methods for Celloidin Sections. 



325. Summers' Ether Method (Amer. Mon. Mic. Journ., 1887, 

 p. 73; Zeit. f. wiss. Mik., iv, 4, 1887, p. 482; Journ. Roy. 

 Mic. Soc., 1887, p. 523). Besides the method given above 

 ( 315), which is applicable to celloidin sections, but is 

 needlessly complicated, Summers recommends the following 

 simpler method. Place the sections in 95 per cent, alcohol 

 for a minute or two, arrange on the slide, and then pour over 

 the sections sulphuric ether vapour, from a bottle partly full 

 of liquid ether. The celloidin will immediately soften and 

 become perfectly transparent. Place the slide in 80 per cent, 

 alcohol, or even directly in 95 per cent, if desired. The 

 sections will be found to be firmly fixed, and may be stained 

 if desired. 



SCHIEFFERDECKER (Zeit. f. wiss. Mik., v, 4, 1888, p. 507) re- 



