214 SERIAL SECTION MOUNTING. 



.j iv, 4, 1887, p. 482) also employs a dry layer of collodion, 

 which he renders adhesive after the sections are arranged on 

 it, by wetting with a mixture of equal parts of alcohol and 

 ether. As soon as the mixture has evaporated, the sections 

 are found to be fixed. 



326. Strasser's Collodion-Paper Method (Zeit.f. wiss. Mile., iii, 3, 

 1886, p. 346). This is an extremely complicated modification of Weigert's 

 collodion method for celloidin sections (post, 340). It is certainly too 

 elaborate to have any chance of supplanting, for ordinary work, the classical 

 methods of preparing series on slides. And it is only adapted for use with 

 Strasser's very complicated " Schnitt-Aufklebe-Mikrotom," or automatic 

 section-fixing microtome. The descriptions of the process and the microtome 

 already published by Strasser would fill a small volume, and cannot be 

 properly abstracted in the space at my disposal here. See the original 

 papers in Zeit.f. wiss. Mik., iii, 3, 1886, p. 346; vi, 2. 1889, p. 154 ; vii, 3, 

 1890, p. 290 ; ib., p. 304; and ix, 1, 1892, p. 8 ; see also a very short abstract 

 of the last paper in Journ. Roy. Mic. Soc., 1892, p. 703, in which is a figure 

 of the "Schnitt-Aufklebe-Mikrotom." 



327. The Shellac Method (GIESBRECHT, Zool Am., 1881, p. 484). 

 Prepare a stock of slides covered with a thin and even film of shellac. This 

 is done as follows : Make a not too strong solution of brown shellac in abso- 

 lute alcohol, filter it thoroughly ; warm the slides, and spread over them a 

 layer of shellac by means of a glass rod dipped in the solution and drawn 

 once over each slide. Let the slides dry. 



Just before beginning to cut your sections take a prepared slide and brush 

 it over very thinly with kreasote applied by means of a brush ; this forms a 

 sticky surface on which the sections are now arranged one by one as cut, 

 care being taken to bring them on to the slide with as little surrounding 

 paraffin as possible. 



When all the sections are arranged the slide is heated on a water-bath for 

 about a quarter of an hour at the melting-point of the paraffin ; this causes 

 the paraffin to run down into a thin layer, and allows the sections to fall 

 through it and come into close contact with the shellac film, whilst at the 

 same time it evaporates the kreasote. 



The slide is allowed to cool, and the sections are now found to be firmly 

 fixed in the shellac. The paraffin is dissolved away by dropping turpentine 

 on to the sections, which are then mounted in Canada balsam. There is no 

 danger of the sections being floated away by the turpentine, because turpen- 

 tine does not dissolve shellac. 



In the note in the Zool. Am. above quoted, the shellac solution is stated 

 to be prepared with common brown shellac (choosing, of course, by prefer- 

 ence the paler sorts), on account of the insolubility of white shellac in 

 alcohol. In the Mitth. d. Zool. Stat. of Naples, of the same year, " bleached 

 white shellac" is recommended to be dissolved as before, in absolute alcohol. 

 In the Journ. Roy. Mic. Soc. (N.S.), vol. ii, 1882, p. 888, it is stated (on 



hose authority is not clear) that the solution is made by mixing 1 part of 



