164 



PRACTICAL HISTOLOGY. 



water and so stiffen the gum. Lastly, remove the paper, 

 imbed in paraffin, and make sections. 



d. The gum may be readily removed from the sections 

 by immersion for some time in water. 



302. Microtome. In making hand-sections with such 

 a knife as a razor, success depends on the steadiness of the 

 operator. It is, however, always difficult to hold the tissue 

 and the knife perfectly steady, and when a large section is 

 wanted say of kidney, spinal cord, or brain a great many 



FIG. 58. The freezing microtome. 



sections have to be thrown away as imperfect. This diffi- 

 culty is overcome by employing a microtome. Various 

 microtomes have long been in use. These, however, it is 

 unnecessary to describe, for the freezing microtome invented 

 by the author presents advantages which were not possessed 

 by any previous instrument. 



The freezing microtome (Fig. 58) consists of a plate of 

 gun-metal (B), with a circular opening in its centre. The 

 opening leads into a well (A), closed inferiorly by a brass 



