CHAPTER VIT. 



IMBEDDING METHODS INTRODUCTION. 



136. Imbedding Methods. The processes known as Im- 

 bedding Methods are employed for a twofold end. Firstly, 

 they enable us to surround an object, too small or too delicate 

 to be firmly held by the fingers or by any instrument, with 

 some plastic substance that will support it on all sides with 

 firmness but without injurious pressure, so that by cutting 

 sections through the composite body thus formed, the in- 

 cluded object may be cut into sufficiently thin slices without 

 distortion. Secondly, they enable us to fill out with the im- 

 bedding mass the natural cavities of the object, so that their 

 lining membranes or other structures contained in them may 

 be duly cut in situ ; and, further, they enable us not only to 

 surround with the supporting mass each individual organ or 

 part of any organ that may be present in the interior of the 

 object, but also to fill with it each separate cell or other 

 anatomical element, thus giving to the tissues a consistency 

 they could not otherwise possess, and ensuring that in the 

 thin slices cut from the mass all the minutest details of 

 structure will precisely retain their natural relations of 

 position. 



These ends are usually attained in one of two ways. Either 

 the object to be imbedded is saturated by soaking with some 

 material that is liquid while warm and solid when cold, 

 which is the principle of the processes here called Fusion 

 Imbedding Methods; or the object is saturated with some 

 substance which whilst in solution is sufficiently fluid to 

 penetrate the object to be imbedded, whilst, after the evapo- 

 ration or removal by other means of its solvent, it acquires 

 and imparts to the imbedded object sufficient firmness for 

 the purpose of cutting. The methods founded on this 

 principle are here called Evaporation Imbedding Methods, 



