CHAPTER VII. 



IMBEDDING METHODS INTRODUCTION. 



136. Imbedding Methods. The processes known as Imbedding 

 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 included object may be cut into sufficiently thin 

 slices without distortion. Secondly, they enable us to fill out with 

 the imbedding 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 evaporation 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. 



In any of these processes the material used for imbedding is 

 technically termed an " imbedding mass." 



There are two chief methods of imbedding the paraffin method 

 and the celloidin or collodion method. 



The paraffin method is the one in most use ; for it is tne more 

 rapid, requiring only hours where the celloidin process requires days 

 or weeks ; and it is the one which the most readily affords very thin 



