Freehand Sections 81 



noticeably dull, for all sections except those cut when the razor is 

 perfectly sharp are sure to be inferior. With softer material the 

 razor may hold its edge for hundreds of sections. Those sections 

 which seem to be worth further treatment should be placed at once 

 in water or in a fixing agent. 1 



With the advent of a cheap, efficient sliding microtome, the 

 hand microtome began to fall into disuse and, today, it has almost 

 disappeared. 



The sliding microtome (Fig. 2) reduces to a minimum the necessity 

 for manual dexterity, but it is a more complicated machine. Study 

 the various parts before you begin to cut sections. How is the knife 

 adjusted? How is the object clamp raised and lowered? How is 

 the thickness of the section determined ? In case of a simple micro- 

 tome like the one shown in Fig. 2, the student should soon answer 

 such questions without any help from the instructor. In case of 

 more complicated microtomes, a demonstration by the instructor 

 will save both time and machine. 



In cutting sections of wood or herbaceous stems, the knife should 

 be set obliquely so as to use as much as possible of the cutting edge. 

 In most cases it is neither necessary nor desirable to cut very thin 

 sections by this method; 10 ju is very thin, and 20, 30, or even 40 /z 

 is usually thin enough. 



Cut with a firm, even stroke, wetting both knife and object after 

 every section. Use water, if the material is fresh; if preserved, 

 use the preservative. Some use a brush in removing sections from 

 the knife, but nothing is quite equal to one's finger; anyone who is 

 in danger of a cut while performing this act is in need of this little 

 practice in manual dexterity. 



WOODY AND HERBACEOUS SECTIONS 



Safranin and Delafield's Haematoxylin. In order to make the 

 directions as explicit as possible, let us follow the processes from 

 collecting the material to labeling the slide. The rhizome of Pteris 

 aquilina is a good object to begin with. Dig down carefully until 

 the rhizome is exposed; then with a sharp knife cut off pieces a few 



1 See chap, ix, last three lines of first paragraph. 



