I. MICROSCOPES. 925 



3645. Description of the apparatus of Prof. Grisebach, from 

 the " Nachrichten von cler Konigl. Gesellschaft der Wissenschaften 

 zu Gottingen." Cuno Rumann, Gottingen. 



3646. Dr. Thoma's Stages (sec also X. 21). 



Rud. Jung, Heidelberg. 



The three stages afford the means of making an exact microscopical exami- 

 nation of the tongue, the mesentery, and the interdigital membrane of the 

 living frog, during the time that these parts are submitted to constant and 

 determinate conditions by a continuous application of salt solutions of known 

 concentration. 



At the same time the apparatus allows continual infusions of different 

 liquids, salt solutions, water, or colouring matters into the vena abdominalis 

 uiediana of the animal. 



For directions for practical use see Virchow's Archives, vol. 65, page 36. 



3647. Querschnitter, an Instrument for cutting under 

 the Microscope. Prof. Dr. V. Jfensen, Kiel. 



The nature and use of the apparatus are given in the accompanying treatise. 

 The instrument only differs from that described in having the curved piece 

 (Biigel) turned forwards. 



3648. Microtome, with steel disc, water-trough, wedge- 

 shaped knife, four moulds. Prof. K. Mobius, Kiel. 



3649. Two Microtomes, with steel disc and three moulds. 



Prof. K. Mobius, Kiel. 



A written explanation accompanies the objects exhibited. 



3650. Five Moist Chambers, for microscopical research 

 (after the designs of Recklinghansen, Ludwig, Geissler, de Bary, 

 and Klebs). Ch. F. Geissler $ Son, Berlin. 



3651. Fritsch's Sliding Microtome. 



Prof. G. Fritsch, Berlin. 



The microtome, of which (on account of some recent alterations) an 

 incomplete account is sent, has on its left a movable box for the reception of 

 the object, on the right a slide (Schieber) with eccentric disc and screw as a 

 holder for the knife. Other knives will be found in the lid for use, accord 

 ing to the degree of resistance offered by the object. 



The object to be cut must be so placed in the metal box that the part to be 

 cut projects over the upper rim. The preparation is imbedded in a suitable 

 mass, or is frozen in a mixture fit for cutting (e.g. Rutherford's). In the 

 brown lacquered box are plates of spermaceti, and mixtures of the latter 

 with cocoa-butter, suitably selected. Some elder pith is imbedded as a 

 specimen. 



After an advantageous position, as regards the object, has been given to 

 the knife, and the box containing the embedded object has been fixed by 

 means of the screws of the large movable box, so that it can be cut by a 

 gentle elevation of the movable box, the screws of the disc and knife are 

 sharply drawn across. Should the position of the object be too low, one of 

 the metal plates furnished with the apparatus is laid under the box, and the 

 screw of the movable box again turned up, but not too tight, in order to pre- 

 vent the strain and pressure on the side of the box becoming too great. The 



