8 THE ELEMENTS OF VEGETABLE HISTOLOGY 



the specimen is held between the thumb and fore- 

 finger of the left hand. The forefinger serves as a 

 support for the flat side of the razor and the thumb 

 should be a safe distance below the level of the block 

 so as to avoid accident. The razor, held in the right 

 hand, is drawn obliquely across the block, making a 

 complete slice of supporting material and specimen. 

 Moistening the block with a mixture of glycerin, 

 alcohol and water is advisable, and the sections should 

 be transferred to this liquid as soon as cut. 



Microtome Sections. The microtome is a mechan- 

 ical device for cutting sections. It consists of a clamp 

 to hold the block and knife for cutting the sections. 

 The object-clamp is so fitted 

 that one may cut sections of 

 definite thickness. In the sim- 

 pler forms (Figs. 2 and 3), the 

 hand microtome is used instead 

 of a special blade, and the 

 object-clamp is fitted in a 

 screw-thread, so that the block 

 may be moved to definite dis- 

 tances above the level surfaces 

 upon which the flat side of 

 the section razor rests. The 

 .milled head by which the object- 

 clamp is raised upon turning 

 through the screw-thread is 

 usually graduated in micro- 

 FIG. 2.-Hand Microtome, millimeters. The more com- 



(Spencer.) , . 



plex torms of microtomes may 



be divided into sliding (Fig. 4), and rotary (Fig. 5) 

 types. The sliding microtomes are further sub- 



