234 THE AMERICAN MONTHLY [Aug. 



MICROSCOPICAL MANIPULATION. 



New Method of Preparing Dentine. — In this method, sug- 

 gested by Lepkowski, it is stated that sections of bone or den- 

 tine may be simultaneously softened and stained. The agent 

 used is a modified form of Ranvier's fluid, and is composed of 

 six parts of a 1 per cent watery solution of gold chloride to 

 three parts of pure formic acid. The pieces of teeth, which 

 should be 2 to 4 mm. thick, are placed in this fluid for twenty- 

 four hours ; they are then removed, washed with distilled water 

 and placed in a mixture of gum arable and glycerine for twenty 

 four hours. On removal from this last re-agent, they are again 

 washed with distilled water, then in alcohol, after which they 

 are embedded in celloidin or paraffin. — Journal British Dental 

 Association. 



To Prevent the Reddening of Canada Balsam. — The ten- 

 dency of Canada balsam to beco me red may be checked, and the 

 balsam bleached by the addition to the solution of a few crys- 

 tals of pure metallic copper, precipitated from copper sulphate 

 solution by any of the ordinary methods. This process origi- 

 nated with the late Allen Y. Moore, of Cleveland, Ohio, and was 

 the result of accident. What the philosophy of it is we do not 

 know, as the copper crystals do not seem to be changed in any 

 manner, even after long immersion in the solution of balsam. — 

 National Druggist. 



Structure of Bacteria. — Sjobring has worked with the Bacil- 

 lus anthracis, a hay bacillus, a vibrio, and several forms of cocci. 

 He fixed the preparations by means of nitric acid, with or with- 

 out alcohol, and stained with carbol-methylen blue or carbol- 

 magenta red, afterwards decolouring with nitric acid and exam- 

 ining in glycerine and water. — Centr. f. Bakt. u. Parasit. 



Formula for Making Picro-Carmine Stain. — (1) Carmine, 

 1 grm. ; liquor ammonia, 4ccm. ; mix and add 5 grms, picric acid ; 

 (2) carmine, 15 grms. ; picric acid, concentrated solution. Agi- 

 tate the mixture (1) from time to time for 2 days, let it settle, 

 decant, and evaporate decanted liquor at ordinary temperature, 

 re-dissolve the dry residue in water, making 1 per cent or 2 per 

 cent solution ; filter when necessary. Triturate the carmine in 

 water until very fine, add enough ammonia to dissolve the car- 



