SECTIONS. 



I2 3 



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

 (y* J* to 40 ;"). By substituting a wide knife-carrier, sections several centimeters in 

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

 rial may be cut. By loosening 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 

 tracing the edges of the paraffin blocks. 



B 



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 intervals. That way which has given the writer 



*Fic. 114. A. Knife for serial sections, furnished with the Reinhold-'Giltay 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 'ft. 



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. 



