CHAPTER XXV 

 MACERATION, DIGESTION AND CORROSION 



MACERATION 



554. Methods of Dissociation. It is sometimes necessary, iri 

 order to obtain a complete knowledge of the forms of the elements 

 of a tissue, that the elements be artilicially separated from their 

 place in the tissue and separately studied after they have been 

 isolated both froin neighbouring elements and from any interstitial 

 cement substances that may be present in the tissue. Simple 

 teasing with needles is often insuflicient, as the cement-substances 

 are frequently 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, by which is meant prolonged soaking 

 (generally for days rather than hours) in media which have the 

 property of dissolving, or at least softening, the cement sub- 

 stances 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 tapj^ing, which last gives in many cases (many epithelia, 

 for instance) 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 wax. By tapping the cover with a needle it is 

 now gradually pressed down, whilst at the same time the cells 

 of the tissue are segregated by the repeated shocks. When the 

 segregation has proceeded far enough, mounting medium may be 

 added and the mount closed. 



A good material for making wax feet is obtained (Vosseler, 

 Zeit. wiss. Mik., vii, 1891, p. 461) by melting white wax and 

 stirring into it one-half to two-thirds of Venice turpentine. 



The most desirable macerating media are those which, whilst 

 dissolving intercellular substances, do not attack the cells them- 

 selves. Those which contain colloids have been found to give 

 the best results in this respect. Iodised serum is an example. 



555. Iodised Serum (Chap. XXI). The manner of employhig 

 it for maceration is as follows : A piece of tissue smaller than a 

 pea must be taken, and placed in 4 or 5 c.c. of weakly iodised 

 serum in a well-closed vessel. After one day's soaking the 

 maceration is generally sufficient, and the preparation may be 



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