ZOOLOGY AND BOTANY, MICROSCOPY, ETC. 



317 



hot mixture. The imbedding substance can be preserved cold in corked 

 vessels for an indefinite time, and will melt at a temperature of about 

 40° C. 



By this means perfectly clear transparent imbeddings may be 

 obtained, which can be cut with the greatest ease after hardening in the 

 cold, and can be preserved unchanged in a vessel over fused calcium 

 chloride, which renders them somewhat harder and therefore better. 

 Very minute objects may be imbedded still more quickly by placing 

 drops of the material on a cork, laying the object on them, and adding 

 another drop of the material. Small quantities of the solution of soap 

 harden completely in a quarter of an hour. For harder parts of plants 

 the process is not very convenient, the material being not sufficiently 

 solid; paraffin or celloidin are better. For making the sections 

 Thoma's slit-microtome was used. 



Dale's Microtome. — Mr. H. F. Dale has patented the microtome 

 shown in figs. 60 and 61, the primary object he had in view being " to 

 provide an instrument which, while it may be made at comparatively 



6 C 



Fig. 60. 



i 



A 





fh 



(UJ-/ 



n 



small cost, shall be effective and durable to the highest degree possible, 

 and which particularly distinguishes itself also owing to the facility 

 with, and advantageous manner in which it is operated." 



The device comprises a base-plate A, upon the surface of which is 

 fixed a rectangular box B, having a freezing chamber a perforated at 

 the bottom with two holes, into the larger of which is secured a tube b, 

 which contains the object. The smaller perforation is provided with a 

 short length of tube c, which serves to drain off the liquefied refrigerant. 

 On the top of the box B is a face plate C, partially covering the box, 

 the open portion 6 1 allowing of the introduction of the refrigerant. 



The mechanism for raising the object comprises a spindle D, to the 

 centre of which is fixed a rachet-wheel E, into the teeth of which a 



1888. z 



