836 SUMMARY OF CURRENT RESEARCHES RELATING TO 



The procedure for imbeddiDg is as follows. A mixture of equal 

 volumes of f;lycerin and 96 per cent, spirit are heated in a water-bath 

 from 60^-70° C. Into this are dropped as many small pieces of glycerin 

 soap as will dissolve. The vessel best suited for the foregoing is a 

 flask, the neck of which may be plugged with cotton-wool in order to 

 prevent the spirit from evaporating too rapidly. The liquid thus 

 obtained is yellow and transparent, but with a slight opalescence. It is 

 then poured into a capsule or paper box. While it is still warm the 

 object to be cut, and which has been removed from strong spirit, is fixed 

 in the desired position by means of needles until the soap has solidified. 

 Large pieces must be soaked for some time in a cold saturated solution 

 of soap before they are removed to the hot fluid. 



The imbedding mixture, which should be kept in a stoppered bottle, 

 melts easily at about 40^ C. 



Very small objects may be readily imbedded by placing them in a 

 drop of the warm solution on a cork, and then covering them with 

 another drop. These small quantities of soap get quite hard in about a 

 quarter of an hour. 



The sections are easily freed from the soap by merely washing them 

 in lukewarm water, while the alkalinity of the soap aids in clearing up 

 the specimen. 



In practice it is found advisable to use two solutions, one for firm, 

 the other for delicate objects. The ingredients of the former are : — 90 per 

 cent, spirit, 32 ccm. ; pure glycerin, 32 com. ; soap, G4 gr. The second 

 contains only 32 ccm. of soap, and is consequently much softer. The 

 harder mass may be sectioned in a Kanvier microtome. 



Dextrin Mucilage for Imbedding.* — For those who use the freezing 

 microtome it will be found useful, in the present high price of gum- 

 arabic, to know that gum dextrin answers just as well as the latter, and 

 costs only about one-fifteenth as much. Mr. T. L. Webb writes upon 

 this point to the 'Provincial MedicalJournal' as follows: — "I find that 

 by making an aqueous solution of carbonic acid (about 1 part of the acid 

 to 40 parts of water) and dissolving therein sufficient dextrin to make a 

 thick syrup, a medium is obtained which is superior to the time-honoured 

 gum and sugar in three ways. It freezes so as to give a firm support 

 Avithout becoming too hard ; it keeps better than gum, in which several 

 kinds of fungi are apt to grow ; and it is much cheaper, costing only 

 about fourpence per pound, while powdered gum acacia costs five 

 shillings. Dextrin dissolves but slowly in cold water, so that a gentle 

 heat is advisable when making the mucilage." 



Wilks' Improved Microtome-j — Mr. G. Wilks describes an improved 

 form of microtome designed by himself, the principal feature of which is 

 that the cutting-plate, or head, is removable ; it is fitted to the lower 

 part by a socket-joint, and secured either by a bayonet-catch or a screw. 

 The hole in the plate or head is bored taper, and is 1/16 in. less in 

 diameter at the outside than in the well or tube of the microtome, thus 

 efiectually counteracting the effect of shrinkage in the imbedding 

 material. The diameter of the well is also much less than in the older 

 form of microtome. 



* St. Louis Jled. and Sur;,'. Jouru., Ivii. (188'J) pp. 231-2. 

 t Trans. Manchester Micr. Soc, 1888, pp. 86-7. 



