AND HOW TO USE IT. 241 



tine after again warming. When .sections of objects have to be 

 made so delicate that there is danger of their falling to pieces 

 after cutting, the object must be left in the warmed glycerine- 

 gelatine until it is thoroughly penetrated by the latter. The 

 gelatine may be removed from the tissues by a fine jet of warm 

 water after the section is made and placed on the slide. For 

 embedding hard tissues, it is an excellent medium. Any degree 

 of hardness may be imparted to the tissues by treating with abso- 

 lute alcohol, the time required for this being from ten to thirty 

 minutes. It is so transparent that the precise position of the 

 object can be seen. In my opinion, it is one of the very best 

 medias for this work. 



Celloidin Method of Embedding Sections.— This is a pure 

 pyroxiline, free from all organic constituents, and makes a clear 

 solution free from all sediment when dissolved in equal parts of 

 95 per cent, alcohol and sulphuric ether. It is. manufactured by 

 Shering, of Berlin, and can be obtained from Zimmermann, 

 Mincing Lane, London, E.G., either in a solid or fluid form. The 

 fresh tissue, suitably divided, is hardened, as usual, in either 

 Miiller's fluid or alcohol, but is allowed to remain forty-eight hours 

 in absolute alcohol, from which it is taken and placed in sulphuric 

 ether for two days. It is then placed in a thin solution of cel- 

 loidin for the purpose of soaking it through thoroughly ; seven to 

 ten days accomplishes this. If very thin sections are wanted, the 

 pieces must be small. If large, the pieces should be of the 

 required size and very thin, so as to allow the celloidin to pene- 

 trate easily. Remove to paper boxes, which are filled with this 

 solution and exposed to the air. When the ether and alcohol 

 have evaporated, a crust forms on the surface. Immerse the 

 boxes in a mixture of methylated alcohol and water. Leave them 

 floating in this for about three days, then the celloidin becomes 

 very solid, though elastic, and firmly embeds the specimens. 

 They are now ready for cutting. Specimens prepared thus may 

 be stained in the different fluids when cut. Care should be taken 

 when clearing them not to use oil of cloves or absolute alcohol, 

 for both dissolve the celloidin. Use alcohol of 95 per cent, and 

 oil of bergamot, origanu;n, or sanders. Where origanum oil is 



Vol. VI. K 



