240 MACERATION AND DIGESTION. 



CHAPTER XXIII. 



MACERATION AND DIGESTION. 



Maceration. 



495. Methods of Dissociation. It is sometimes necessary, in 

 order to obtain a complete knowledge of the forms of the 

 elements of a tissue, that the elements be artificially separated 

 from their place in the tissue and separately studied after 

 they have been isolated both from neighbouring elements 

 and from any interstitial cement-substances that may be 

 present in the tissue. Simple teasing with needles is often 

 insufficient to effect the desired isolation, as the cement-sub- 

 stances are often tougher than the elements themselves, so 

 that the latter are torn and destroyed in the process. In this 

 case recourse must be had to maceration processes, by which 

 is here meant treatment with media which have the property 

 of dissolving or at least softening the cement substances or 

 the elements of the tissue that it is not wished to study, whilst 

 preserving the forms of those it is desired to isolate. When 

 this softening has been effected the isolation is completed by 

 teasing, or by agitation with liquid in a test-tube, or by the 

 method of tapping, which last gives in many cases (many 

 epithelia for instance) admirable results which could not be 

 attained in any other way. The macerated tissue is placed 

 on a slide and covered with a thin glass cover supported at 

 the corners on four little feet made of pellets of soft w;i.\. 

 By tapping the cover with a needle it is now gradually pressed 

 down, whilst at the same time the cells of the tissue are segre- 

 grated by the repeated shocks. When the segregation has 

 proceeded far enough, mounting medium may be added, and 

 the mount closed. 



The student will do well not to neglect tin's Dimple method, 

 which is one that it is most important to bu acquainted with. 



