706 SUMMARY OF CURRENT RESEARCHES RELATING TO 



used for fixing the cover passing under it and re-dissolving the 

 background, a remedy for which is to employ a background having 

 a solvent difierent to the cement used for fixing the cover. 



Dry Mounting.*— Mr. F. French has contributed to the Postal Micro- 

 scopical Club a slide mounted in a style which promises to be useful for 

 certain kinds of opaque objects which will bear occasional exposure to 

 the dust and moisture of the air, and which are best viewed without 

 the intervention of a cover-glass. The slip is composed of cardboard, 

 cut to 3 X 1 inches, the required thickness in each case being obtained 

 by building up a sufficient number of thicknesses, gummed together. 

 The centres are punched out as from the paper covers for glass slips, 

 and the object is fastened at the bottom of the cell thus formed, either 

 upon mica fastened at the bottom of the cell, or upon a bottom card 

 not punched like the rest. The object is covered by a rectangular 

 brass sliding-plate below the upper card, the card next below being 

 cut away to receive it and to allow it room to slide entirely away from 

 sight when desired, A pin-head is rivetted and soldered into this brass 

 plate, and projects through the upper card, appearing near the right 

 end of the finished mount, through a longitudinal slot that permits it 

 to be pushed toward or from the other end of the slide, and thus to 

 carry the brass plate over the object or away from it. The whole 

 mount is finished by covering with paper in the old style. 



Semper's Method for Dry Preparations.t — Herr Semper recently 

 exhibited to the Wurzburg Society some zoological and anatomical 

 preparations which had been prepared by a new method for dry 

 preservation. 



After being hardened in a solution of chromic acid, the objects are 

 placed in alcohol to remove the water, and afterwards steeped in oil of 

 turpentine and finally dried. The tissues whilst drying are permeated 

 by innumerable small air-bubbles, and in consequence the prepara- 

 tions retain their original form without sensibly shrinking, whilst in 

 colour they assume a white tint similar to that of a gypsum model. 

 The finished preparation, which is almost pure white, and which pos- 

 sesses a firm leathery consistency, may be painted with colours in 

 parts as may be required for teaching purposes. The preparations 

 produced were partly complete animals — mussels, Annelida, &c. — with 

 the viscera of various vertebrate and invertebrate animals. A prepa- 

 ration of a cat's eye showed that, after drying, the position of the 

 parts — the lens, ciliary processes, &c. — underwent no change. A 

 microscopical preparation of brain treated on this method proved that 

 still simpler microscopic relations were retained after the drying, and 

 — particularly with carmine colouring — could be distinctly recog- 

 nized. 



Herr v. Kolliker pointed out the advantage to be derived from 

 this method, especially the possibility of adapting the preparations for 

 special demonstration by painting. 



* Amer. Natural., xv. (1881) p. 346. 



t Verb. Phys.-Med. Gcsell. Wurzburg, xv. (1881) SB. ix. 



