776 SEC. 18. BIOLOGY. 



3610. Instruments for Microscopical Researches, in 

 box. Prof. Dr. Leonard Roesler, Klosterncuburg. 



3611. Instruments for Microscopical Researches on 



living organisms, adapted to their observation when under the 

 influence of various gases and at different temperatures. In box. 

 Prof. Dr. Leonard Roesler, Klosterneubury. 



3612. Drawings illustrating preceding Apparatus. 



Prof. Dr. Leonard Roesler, Klosterneuburg. 



3613. Freezing Apparatus. A simple form for preparing 

 soft tissues for microscopical examination, consisting of a solid 

 copper cylinder with wooden handle and felt cap to fit over 

 cylinder. Dr. Urban Pritchard. 



Mode of use : Immerse cylinder in mixture of ice and salt for a few 

 minutes ; then remove and wipe, place tissue, to be cut, after being moistened 

 with gum, on metallic end. Put felt cap over cylinder ; tissue will be frozen 

 and ready for cutting in two or three minutes. 



3614. Glass Microtome for microscopical sections of 

 hardened or frozen tissues. Dr. M. E. Mulder, Groningen . 



The hardened tissue, previously imbedded in a cylindrical mass of wax, 

 consisting of a mixture of Stearine - - 30 



Hogs lard - - 24 



White wax - - 16 



is introduced into the glass tube of the microtome, which is polished at 

 its upper margin. 



An}- rotation or movement of the wax cylinder, which is exactly of the same 

 size as the tube, is prevented by the four pins. The wax cylinder can be 

 moved up or down by means of a screw, and sections are made by passing a 

 knife over the polished surface of the tube. 



The thickness of the sections is indicated by the lines on the screw. (Every 

 line is -fa mm.) 



When the microtome is used for freezing, the glass tube is unscrewed and 

 replaced by the freezing box. The tissue, imbedded in a solution of gum 

 arabic, is frozen by filling the freezing-box with snow or ice and salt. 



3615. Kratometer for finding magnifying power and focal 

 length of objectives. Dr. Royston Pigott, F.R.S. 



This simple instrument is so contrived that whatever object glass is used, 

 the actual power is ascertained at once, whatever be the length of body em- 

 ployed. A stage micrometer of lines ruled to lOOths and l,000ths of an 

 inch is viewed by the kratometer eye-piece, and the number of divisions of the 

 stage micrometer embraced by ten of the kratometer, gives exactly the 

 magnifying power, if multiplied by ten. This instrument at once determines 

 the focal length and comparative powers of all object-glasses submitted to 

 this test. 



3616. Microscopic Refractometer for ascertaining the 

 mean refractive index of plates of glass or lenses. 



Dr. Royston-Pigott, F.R.S. 



A new refractometer for determining the refractive index of white light 

 (or mean rays or line E in the solar spectrum) of small plates or lenses of 



