276 Modern Microscopy 



accomplished by the aid of a drop of xylol, or the like, 

 applied with a brush and wiped off with a clean soft 

 leather below as well as above. It is very important to 

 keep the knife-edge free from stray particles of paraffin ; 

 the presence of such will cause the ribbon to become 

 crooked, will facilitate curling, and, what is worse, will 

 cause longitudinal slits in the sections. If you find a 

 ribbon of sections which began well, suddenly become 

 afflicted with one of the maladies just mentioned, cleaning 

 the knife with xylol will often remedy matters. Another 

 cause of failure is from the knife-edge having become 

 turned with a hard object ; to remedy this, bring another 

 portion of the knife into action. Bear in mind the failures 

 likely to result from bad knife-sharpening. With sledge 

 microtomes the ribbon should be cut into suitable lengths 

 as it is given off. It is well, however, to allow the ribbon 

 to fall over the back of the knife until its end approaches 

 the base of the microtome, then a length should be cut off 

 sufficient to be afterwards cut into two or three lengths for 

 finally mounting. 



Treatment of Ribbon Sections. — The best size of 

 cover-glass for 3 inches by 1 inch slides is I5- inches by 

 -J inch. Supposing, then, that your sections are of such 

 size that three rows of six in a row will be well covered 

 by the cover-glass when mounted, then you cut off from 

 the end of the ribbon with a pair of scissors twelve or 

 eighteen sections, and keep them carefully under cover until 

 all are cut, taking care to remember at which end is the 

 first section, in order that the proper sequence may be 

 maintained in mounting. Be careful when cutting off the 

 lengths to leave five or six sections intact upon the knife, 

 because, if you take away all of them, when cutting is 

 resumed the first few sections will curl again and be lost. 

 It is best to cut all the sections as rapidly as possible when 

 they have been started. If the microtome is left for a 



sections, or place a lamp or Bunsen burner close to the microtome for 

 a few minutes, or alter the inclination of the knife (see p. 244). 



