430 THE AMERICAN MONTHLY [Dec 



is not precipitated on boiling. To this add 1.5 to two per 

 cent of ag^ar-agar, previously soaked in acidulated water, 

 and boil the mixture in a Koch's steamer until the agar- 

 agar is well dissolved. It must now be filtered through a 

 hot water-funnel. The filtrate should be perfectly clear. 

 To the fittrate add four or five per cent of gly- 

 cerine. It may then be poured into test tubes and 

 sterilized. Besides the glycerine, 0.5 to two per cent of 

 grape sugar may be added ; this however generally renders 

 the medium a little darker in color. 



Before adding the caustic potash to the serous fluid, a 

 small quantity of it should be boiled in a test tube. If it 

 becomes practically solid, or contains large quantities of 

 albumin, the fluid must be diluted with at least twice its 

 bulk of distilled water ; and then to every 100 c. cm. of the 

 diluted fluid 2 c. cm. of KOH and 1.5 to two grams of agar- 

 agar are to be added. The serous exudation, after the 

 addition of the alkali, also forms a good liquid nutrient 

 medium for bacteria. 



Storax as a Mounting Medium. — Permanent prepara- 

 tions can be mounted in storax, according to Dr. J. H. Pitf- 

 ard {^Medical Record^ 1895, p, 547), if it be prepared as fol- 

 lows: — The storax is liquified on a water bath, then fil- 

 tered through two or three thicknesses of cheese cloth on 

 a hot-water funnel, and when cold mixed with an equal 

 weight of xylol. Shake well several timesthrough absorb- 

 ent cotton or Swedish filter-paper, and evaporate at a gen- 

 tle heat to the consistency of treacle. Finally, to each 

 two parts of the fluid add three parts of naphthaline mono- 

 bromide, and heat gently until a clear amber-colored fluid 

 is obtained. Preferably, the refractive index of the 

 medium should be brought to 1.625, by adding- more of the 

 ingredient that may be found deficient, and the product 

 will then be found suitable for work with the highest 

 powers. 



Brown Cement, suitable for Microscopic Work. — The 

 Chemist and Druggist recommends either a thick solution 

 of shellac in vegetable naptha, or of gutta-percha in chloro- 

 form or bisulphide of carbon. 



