IMBEDDING MKTHODS ( PARAFFIN). 99 



out of cells by prolonged heating in mixtures of paraffin 

 with chloroform or benzol, or the like ? Indeed, it seems 

 to me that the great point to be attended to in paraffin work 

 of the finer order is to minimise the action of heat. It is 

 therefore important both to employ a paraffin of the lowest 

 melting-point that will give good sections (see below, 141), 

 and to abbreviate the warm bath as much as possible. 



If chloroform or other volatile agent be taken, choice may 

 be rnao^eoftwo methods : either, as in Giesbrecht's method, 

 the chloroform containing the object is heated to the melting- 

 point of the paraffin, and the paraffin gradually added, and 

 the mass kept at the melting-point of the pure paraffin until 

 all the chloroform is driven off ; or, as in Biitschli's method, 

 the objects are simply passed direct from chloroform into a 

 solution of paraffin in chloroform, in which they remain until 

 thoroughly impregnated (half to one hour), and which is then 

 evaporated at the melting-point of the paraffin. Biitschli 

 recommends a paraffin solution melting at 35. (Such a 

 solution is made of about equal parts of chloroform and 

 paraffin of 50 melting-point.) Or, in the case of larger 

 objects, instead of evaporating the chloroform (which is often 

 a very long process, as the chloroform must be completely 

 driven off, or the mass will remain too soft for cutting), 

 Biitschli simply transfers them from the bath of paraffin ! 

 solution to a bath of pure paraffin. 



Giesbrecht's method (Zool. AHZ., 1881, p. 484), more fully 

 stated, is as follows : 



Objects to be imbedded are saturated with absolute alcohol 

 and then brought into chloroform (to which a little sulphuric 

 ether has been added if necessary, in order to prevent the 

 objects from floating). As soon as the objects are saturated 

 wi ch the chloroform, the chloroform and objects are gradually 

 warmed up to the melting-point of the paraffin employed, and 

 during the warming small pieces of paraffin are by degrees 

 added to the chloroform. So soon as it is seen that no more 

 bubbles are given off from the objects, the addition of paraffin 

 mjiv cease, for that is a sign that the paraffin has entirely 

 displaced the chloroform in the objects. This displacement 

 having been a gradual one, the risk of shrinkage of the 

 tissues is reduced to a minimum. 



MAYER (Grundzuge, p. 78) first saturates the objects with 



