ZOOLOGY AND BOTANY, MICROSCOPY, ETC. 107 



C and D are so shaped that when the clearance angle is 10°, the cutting 

 edge of the blade is approximately in line with the centre line of A. 



The fixture described above was all the author had to make for 

 microtome work. The slide-rest was already provided with a boring- 

 tool holder, which is a cast-iron fixture fitting the slide-rest in place of 

 the usual tool-post, and having a ^-in. round hole in it, parallel with the 

 upper slide, and at the same height as the lathe-spindle. This hole is 

 split on one side, and has pinching screws to close the split and clamp 

 the round boring tools securely on the round shank A of the razor- 

 holder. This arrangement admits of turning A on the boring-tool 

 holder, so as to bring the razor edge vertical to give a straight cut, or 

 with an oblique edge to give a drawing cut. C and D may be moved 

 along to different parts of B in order to bring different parts of the 

 cutting-edge into action. When necessary to loosen C and D, this is 



Fig. 18. 



done while the razor is clamped in place, so that C and D will be properly 

 located in regard to each other. 



This fixture in conjunction with a lathe makes a fairly good micro- 

 tome, if the requirements are not too exacting, as it cannot be used for 

 the best or for riband work. 



Triepel's Cylinder-Rotation Microtome.* — This has been designed 

 by H. Triepel, and is made by the firm of Gr. Miehe, of Hildesheim. It 

 is shown in fig. 19 one-third of the full size. A strong-walled hollow 

 cylinder, 107 mm. external diameter, is firmly connected with a base- 

 plate. The cylinder is supported on three uprights, and within it is a 

 second hollow steel cylinder, 115 mm. in height and 80 mm. in external 

 diameter. Its upper and lower ends are both closed by brass plates. To 

 the under plate a small disk of hardened steel is screwed on, by means of 

 which the inner cylinder rests on the micrometer screw. The steel cap 

 of the screw is also hardened. The raising arrangement is of the usual 

 kind. Rotation through the space of one tooth raises the cylinder 2 /i. 

 The object-holder is secured on the upper plate of the inner cylinder. 



* Zeitschr. wiss. Mikrosk., xxii. (1905) pp. 118-25 (3 figs.). 



