ZOOLOGY AND BOTANY, MICROSCOPY, ETC. 889 



The wash is made with a small brush drawn backwards and forwards 

 until the entire surface has been moderately but evenly wetted with 

 the oil. 



Sections are now cut and arranged for the first cover ; this done, 

 the slide is warmed over a spirit-lamp so that the paraffin adhering 

 to the sections melts and flows together, forming an even layer, which 

 cools almost instantly, and thus secures the position of the sections 

 while those of the second cover are prepared. The sections for the 

 last cover having been completed, the slide is warmed for ten minutes 

 on a water bath, in order that the sections may sink into the shellac 

 and become fixed, and the oil of cloves evaporate. After allowing 

 the slide to cool the process is concluded by washing away the 

 paraffin with turpentine, and mounting in balsam dissolved in 

 chloroform. 



The following mode of fixing sections is described by Dr. J. 

 Gaule*: — 



The sections are cut dry and placed on the slide in the order and 

 position in which they are to be mounted. 



They are then smoothed out by the aid of a fine brush wetted in 

 50-60 per cent, alcohol, until all wrinkles are removed and every 

 part is in close contact with the slide. 



The slide is allowed to stand several hours (or over night) until 

 the alcohol has completely evaporated, and the sections are left 

 adhering quite firmly to the glass. The process may be hastened by 

 gently warming to 45-50° C. 



The paraffin may be removed by any of the solvents in common 

 use, but xylol is recommended. A few drops are allowed to flow 

 over the sections, and after a few moments the paraffin is fully 

 dissolved. 



The balsam (a mixture of balsam and xylol in equal parts) is 

 placed on the cover-glass, and this allowed to sink slowly, from one 

 side, over the sections. 



Dr. Gaule finds it convenient, especially with serial sections, to 

 use large cover glasses — often nearly as large as the slide itself. 

 Thus a single slide may often contain a large number of sections 

 closely arranged under one cover. 



For large sections this method offers one important advantage 

 over that of Dr. Giesbrecht ; by the former all wrinkles may be 

 removed, while by the latter the sections must lie as they fall. In 

 the case of smaller sections, not liable to get wrinkled during the 

 placing, Mr. Whitman t prefers the shellac method. 



Eau de Javelle for Removing the Soft Parts of Preparations.! 

 — Dr. F. C. Noll has found eau de javelle (subchloride of potassium 

 KC20) very suitable for preparations of Spongilla, and for destroying 

 the protoplasm in other objects. 



If siliceous sponges are burnt or boiled in potash the hard 

 parts, spicules, &c, separate, and are not shown in their proper 



* Arch. f. Anat. u. Phys., 1881, Phys. Abthlg., p. 156. Cf. also this Journal, 

 ante, p. 428. 



t Loc. cit. \ Zool. Anzeig., v. (1882) pp. 528-30. 



