18 The Freezing Microtome. 



amount of pressure to be put on the razor will depend 

 on the tissue imbedded and can only be learnt by prac- 

 tice. As each section is cut dip the razor into the cap- 

 sule of spirit and wash it off. Wipe the razor occa- 

 sionally and remove adhering portions of wax mass, 

 and always keep the edge wetted with spirit. When a 

 sufficient number of sections have been cut, the thin- 

 est should be selected and removed to a watch glass 

 containing clear spirit. 



Great care is required in cutting sections by hand, to 

 hold the razor firmly yet lightly, so as to cut them thin 

 and at the same time even, and this cannot be done 

 without a great deal of practice. 



For larger sections the boxes must be proportionately 

 increased in size, and it will be found convenient when 

 the wax mass is as wide or wider than the razor to cut 

 off slices from each side so as to reduce the surface to 

 be cut as much as possible without interfering with the 

 stability of the imbedded material. 



A small flat spear-headed needle will be found useful 

 for taking up very small sections. 



THE FREEZING MICROTOME. 



A much easier method of cutting sections is by using 

 a microtome. Of these there are a number made, in 

 some of which the material is imbedded in wax mass, 

 or a mixture of paraffin and lard, and raised gradually 

 by a screw, while a razor is worked on a flat plate 

 shaving off sections ; these are also made with a cham- 

 ber to contain a freezing mixture, so that the material 

 can be imbedded and frozen. 



