264 On Cutting Sections of Animal Tissues 



It should be placed on a flat piece of cork and filled with the melted 

 mass, sufficiently to cover the piece of tissue ; as soon as the wax 

 mixture begins to solidify around the edges of the box, the tissue is 

 to be introduced as follows : * — " A needle is stuck slightly into the 

 end opposite to that from which sections are to be cut, and the bit 

 is plunged into the mass with its long diameter horizontal, and in 

 such a position that the end furthest from the needle is near, but 

 not in contact with, the side of the box, and consequently the other 

 end is at a cou skier able distance from the side. In this way, 

 although the whole is surrounded with the wax mass, there is a 

 greater thickness around the end into which the needle is stuck, so 

 that the whole can be securely and conveniently held." By 

 passing the needle directly through the tissue and into the cork 

 upon which the box rests, "the operator is saved the trouble of 

 holding the needle till the wax mixture solidifies. In finally with- 

 drawing the needle, the greatest care must be taken to give it a 

 twisting motion, as otherwise, especially if the object is thin, it is 

 apt to be displaced." " If a thin membrane is to be embedded, of 

 such tenuity that a needle could not be introduced without danger 

 of destroying it, the following method may be used: — A box is 

 half filled with the mass, and then, as soon as it begins to solidify, 

 the membrane is applied to the half solid surface ; the box is then 

 filled with a thoroughly fused mass, care being taken that it is not 

 too hot." In embedding any of the fatty masses, great care should 

 be taken that the surfaces of the piece are dry previous to immersion 

 in the mass, otherwise the medium will not adhere to it. 



Besides the media already mentioned, others, as gum,f and a 

 mixture of gelatine and glycerine, $ have been used for some tissues 

 with great success. The first is prepared by making a clear 

 concentrated solution of the pulverized gum acacia. The gelatine 

 mixture is prepared as follows : — Two parts of concentrated solution 

 of isinglass and one part of pure glycerine. It is not necessary to 

 place the tissues in alcohol previous to embedding in these. A 

 paper box or cone having been prepared, it is rilled with the 

 mixture — the gum cold, the gelatine hot ; the piece of tissue is then 

 thrust into it. The gelatine mass when cold becomes solid. Both 

 are then placed into common alcohol until a sufficient degree of 

 hardness is attained; on releasing them from the paper they are 

 ready for further treatment. 



When cavernous structures, as lung-tissue, cochlea, &c, are 

 embedded by the foregoing methods, good sections cannot always be 

 obtained, in consequence of the tissue not being supported within, 

 as well as without ; but if it be placed in any one of the melted 



* Klein, in ' Handbook for the Physiological Laboratory.' 



f Strieker, loc. cit. 



% Klebs in Frey, loc. cit. 



