EMBEDDING MEDIA. 



These are mostly used to support the tissues during the 

 cutting with a microtome. 



The simplest method is that adopted for firm vegetable 

 tissues. A cylinder of carrot is made to fit the microtome, 

 and then divided vertically. The piece of tissue is fitted in 

 between the two halves of carrot ; the carrot and tissue are 

 cut at the same time, the former, of course, transversely. 

 The direction of the latter will depend upon the position in 

 which it is placed in the carrot. Another method is to embed 

 in Paraffin, and fit the block of Paraffin to the microtome. 



Neither of the above are suited for delicate or porous tissues. 

 They must be supported in the interstices by saturation with 

 the embedding material. For this purpose Grum, Celloidin, 

 and Paraffin are used. When it is desired to support in 

 position tissues which would otherwise fall to pieces when cut 

 into sections, Celloidin is generally used. Saturation with 

 Paraffin is mostly employed for serial cutting. 



(i.) GUM (Mucilage). 



Colourless Gum Acacia, 2 ; Cold Water, 3. 

 Dissolve the Grum in the Water, and to each ounce of the 

 solution add 1 grains of Carbolic Acid. 



(ii.) GUM AND SYRUP. 



Mucilage of Acacia, 50 cc. ; Simple Syrup B.P., 30 cc. 



