240 THE MICROSCOPE 



as an easy way of holding a tissue firmly in place, and without 

 injury to it or to the knife. 



Tolu instead of Chloroform for Embedding in Paraffin- 

 Objects embedded in paraffin can be better and more easily cut 

 when they have been previously treated with tolu instead of 

 chloroform. After the object has been hardened in alcohol, it is 

 placed directly into tolu for 24 hours (or less for small objects), 

 and transferred from it to the parafifin-bath, in which it is also kept 

 for 24 hours (Dr. M. Holt).^ 



Embedding Small Objects (Dr. L. Gerlach).— This is very 

 useful for embryos or parts of embryos. Take 40 grammes gela- 

 tine, added to 200 ccm. of a saturated solution of arsenious acid 

 with 120 cc. of glycerine. This fluid must be clarified with white 

 of egg and will remain perfectly clear for years in a well-stoppered 

 botde. Objects hardened in alcohol are most suited for this 

 method of embedding. Prior to embedding, place them for two 

 or more hours, according to their size, in weak glycerine (glyce- 

 rine I part, water 2 parts), to which some thymol has been added. 

 In order to remove all traces of alcohol, the fluidis changed from 

 hour to hour. 



Glycerine and Gelatine.— Alcohol or chromic acid preparations 

 may be placed in a mixture of one volume of a very concentrated 

 solution of isinglass and half a volume of pure glycerine. The 

 whole, when cooled, is to be replaced in chromic acid or alcohol, 

 where they will become sufficiently hard. 



Pure Glycerised Gelatine (Dr. E. Kaiser). — Take finest French 

 gelatine, i part by weight. Steep for about two hours in 6 parts 

 (by weight) of distilled water, and add 7 parts of pure glycerine. 

 Then to every 100 grms. of the mixture, i grm. of a concentrated 

 solution of carbolic acid is added. The whole must be warmed 

 for ten or fifteen minutes, stirring all the while until the flakes 

 produced by the carbolic acid have disappeared. Then filter 

 while still warm through the finest glass, previously washed in dis- 

 tilled water. When cold, the preparation can be used like Canada 

 balsam. This medium is also an excellent embedding substance. 

 For this purpose the objects must be placed in the glycerine-gela- 



* Zool. Anseig., viii., 1885. 



