1890] NRW-YORK MICROSCOPICAT. SOCIETY. 57 



The consecutive steps here described are for .objects already 

 stained. For enclosing the sections in a film of collodion, 

 there is needed, in the first place, a thin paper of even surface, 

 and evenly saturated with- the smallest sufficient quantity of 

 wax or paraffin. This treatment will prevent the solution of 

 collodion from entering the body of the paper. Two solutions 

 of collodion of different composition are used. No. i consists 

 of two parts of collodion and one part of castor-oil. No. 2 con- 

 sists of equal parts of each, all by weight. By means of a large, 

 soft brush a coat of collodion. No. i, is spread upon the paraffin- 

 paper. On this coat the sections, intended to be enclosed, are 

 laid in order, where they receive a full coat of collodion, No. 2, 

 the presence of air-bubbles being carefully avoided. Then, 

 before bubbles of ether in the interior of the collodion may 

 begin to form, the paper, carrying collodion and sections, is 

 immediately immersed in a bath of spirit of turpentine. The 

 spirit of turpentine hardens the collodion, by extracting the 

 ether, alcohol and castor-oil contained in the solution. Slightly 

 warming the bath quickens the process. The coating of col- 

 lodion, after immersion in turpentine, first appears milky white, 

 but presently it becomes transparent and colorless, and then the 

 hardening is done. 



Now the film of collodion lies isolated in the paper, out of 

 which the paraffin or wax is dissolved by the turpentine. If, 

 while laying the sections on the collodion, a small piece of 

 paper, bearing the number of the adjoining section, is occasion- 

 ally inserted, this also is enclosed in the film and helps to dis- 

 tinguish sections afterwards desired. The film being hardened 

 and isolated, sections desired for permanent mounting and 

 inspection can be easily selected. They are cut out by means 

 of scissors or knife, and mounted in the regular way in balsam, 

 noting the number or other mark of any section on the label of 

 the slide. 



The sections not selected for immediate permanent mounting 

 must then be enclosed in rosin for preservation. To do this 

 take the strips of paper, on which the collodion films rest, out 

 of the turpentine bath ; let the oil drain off as much as possible; 

 transfer them to filtering paper, and remove the surplus oil. 

 The film containing the sections is then covered, by means of a 

 soft brush, with a thick layer of a strong solution of light-colored 



