SECTIONS. 



123 



moves forward at each stroke a distance governed by the set-screw of the scale 

 (/<3 /' to 40 /<). By snbstitnting a wide knife-carrier, sections several centimeters in 

 diameter may be cnt, and by using a slanting knife, as for celloidin, very hard mate- 

 rial may be cnt. By Ioo.sening a set-screw, the razor as here .shown may be turned 

 a few degrees to right or left, and the paraffin block may also be moved through a 

 considerable arc in any direction, it being held securely in any position by pressure 

 of a collar-screw on a ball-and-socket joint. On 72 in plate 13 is an apparatus for 

 trueiirg the edges of the paraffin blocks. 



Fig. 1 14.* 



Collections of living bacteria are also necessary. Fortunately many may now 

 be obtained, as needed, from Krai, in Prague; but, unfortunately, they do not always 

 correspond to their name. Others must be kept on hand, and the cultures (of some 

 sorts) must be renewed at frequent inten^als. That way which has given the writer 



*FiG. 114. — A. Knife for serial sections, furnislied with the Reinhold-'Gihay microtome. This 

 is made by Joseph Rodgers & Son, Sheffield, England. One-half actual size. 



B. Microtome knife made to order by Charles Lentz & Sons, Philadelphia, and found useful in 

 cutting hard material with long slant strokes. One-half actual size. The broad wedge-shaped blade 

 of this knife is shown in !>. 



C. Knife obtained from J. R. Torrey & Co., Worcester, Mass , and found very useful for making 

 serial sections on the microtome. One-half actual size. 



D. Torrey razor, recommended for free-hand sections. The very thin blade is flat on one face 

 and hollow-ground on the other, as shown in d. It is made of the very best steel and holds an edge 

 well. One-half actual size. 



a, b, c, d, end views of the cutting edge of knives shown in A, B, C, D. Actual size. 



