320 MICROSCOPICAL TECHNIQUE. 



Method of Mounting Calcified Microscopic Specimens.*— 



Mr. J. Mansbridge finds the one great disadvantage in the use of 

 fluid balsam as a mounting medium for calcified specimens, where 

 it is advisable to retain the air in the structure for purposes of clear 

 definition, is the liability to run into any spaces, such as lacunae 

 or tubuli that may exist in the tissue. To overcome this difficulty 

 he uses desiccated balsam in the following way : — Take a clean 

 slide, place it upon a hot table with a small lump of balsam upon it, 

 and cover with a hot cover glass, which must be pressed down in 

 such a way as to expel all air from beneath it. Remove the slide 

 to a cool surface and continue to keep pressure upon the cover 

 glass for a few minutes, when the balsam will be found to be quite 

 hard and the specimen ready to be labelled and put away finished. 

 He finds the advantages are : — i. — There is no chance of the 

 mounting medium running in and spoiling the section, as it becomes 

 perfectly hard a few minutes after removal from the hot table. 

 2. — The specimen is finished at the time and is ready for the 

 cabinet. There is no need to use a clip, no fear of the cover glass 

 shifting if the slide is placed upon its side. 3. — It is very con- 

 venient for teaching purposes, as the ordinary stiff balsam soon 

 becomes in a most deplorable condition. 



Cedar-wood Oil.f — This oil possesses a growing importance in 

 connection with its use with optical instruments. For this purpose 

 it is essential that its refractive index should coincide as nearly as 

 possible with that of the lenses with which it comes in contact, 

 and it is usually necessary to condense the oil to some extent. 

 Schimmel's ordinary cedar-wood oil is stated to have a refractive 

 index ND i "50567 at 17*^ which becomes ND 1*5 1682 when the 

 oil is condensed. 



New Multiple Staining Fluid. J— Dr. P. G. Unna differentiates 

 bacilli in tissues by a polychromic methylene blue solution which 

 contains methylene red and violet, in addition to the blue. The 

 sections are transferred from alcohol and allowed to remain in the 

 stain for at least ten minutes. They are then passed through 



* Trans. Odont. Soc, xxv. (1893), PP- 17^ — 177. 



t P/iar. /oicr., April 29th, 1893. 



X Phar. Journ., April 29th, 1893. 



