136 - IMBEDDING METHODS. 



that is a solvent of the imbedding material, as makes it more 

 readily susceptible of infiltration by the latter) ; or the pro- 

 cesses may be based on another principle, namely, that of the 

 employment of substances which whilst in solution are suffi- 

 ciently fluid to penetrate the object to be imbedded, whilst at 

 the same time after the evaporation or removal by other 

 means of their solvent, they acquire and impart to the 

 imbedded object sufficient firmness for the purpose of cutting. 

 The collodion process sufficiently exemplifies this principle. If 

 a piece of soft tissue be dehydrated, and soaked first in ether 

 and then in collodion, and if the ether contained in the collo- 

 dion be allowed slowly to evaporate, the tissue and surrounding 

 mass of collodion will acquire a consistency such as to admit of 

 thin sections being cut from them. 



The egg-emulsion process, in which a mass that is liquid 

 whilst cold is coagulated by heat, forms a class by itself. 



In any of these cases the material used for imbedding is 

 technically termed an " imbedding-mass." (Einbettungs- 

 masse : masse d' inclusion. Imbedding methods are spoken 

 of by French writers as methodes d'inclusion, or mcthodes 

 d'enrobage) . 



266, Imbedding Manipulations. Before proceeding to de- 

 scribe in detail the more important imbedding methods, it is 

 necessary to give an account of the manipulations of the 

 process of imbedding in general. This will serve at the same 

 time for such account a's is needful of the methods of Simple 

 Imbedding these being now relatively quite unimportant 

 and of the stage of imbedding sensu stricto that forms part of 

 the processes of the Infiltration Methods. 



To imbed an object in such a substance as liver or spinal cord (which does 

 not strictly come under the category of an imbedding mass at all, as defined 

 above) nothing more is necessary than to take a piece of fresh liver or cord 

 of convenient dimensions, scoop out in it a hole o the size of the object to 

 be imbedded, place the object in the hole, and immerse the mass in alcohol 

 until such time as the mass is sufficiently shrunken and hardened to hold the 

 object firmly and permit of section cutting. 



If pith be employed, a cylinder of pith is halved longitudinally, a cavity 

 corresponding to the object to be imbedded is made by scooping out the 

 inner face of either half-cylinder, the object placed in position between these, 

 and the cylinder pushed into the well of a microtome (which it should fit 

 accurately), and moistened with alcohol (or other suitable liquid) in order 

 that the pith may swell round the object. It should be noted that it is 

 better to make the cavity in the pitli by simple pressure and knead in f/ (c. g. 



