348 



SUMMARY OF CURRENT RESEARCHES RELATINCt TO 



Fig. 72. 



Fig. 73. 



surface of the brass plate and to within • 5 mm. of the upper surface 

 of the knife-carrier. It has an inner cylindrical piston 15 mm. in 

 diameter and a sleeve around this which may be used with the 

 piston, when it is desired to have a larger well, having a diameter of 

 19 mm. On each side of the brass plate and rising 1 mm. above its 

 upper surface is an iron bar, 7 mm. thick, running the whole length 

 of the bed and screwed fast to it. These are the ways or tracks 

 upon which the knife-carrier slides. The knife-carrier consists of a 

 solid plate of brass, 13 cm. long, 8 • 6 cm. broad, and 8 mm. thick, with 

 projections along both sides, 6 mm. thick and 13 mm. deep, which 

 fit down over the outside of the iron ways. The inside of these 

 projections and the adjoining under surfaces of the brass plate are 

 planed and polished so as exactly to fit over and upon the smooth iron 

 tracks in such a way that the carrier moves freely, but with the 

 utmost precision, back and forth upon them. 



The brass plate A has an oblong opening cut in its middle, 9 • 6 

 cm. long and 3-3 cm. wide, through which, when in place, the 

 cylindrical object-holder projects, very nearly to the upper surface 

 of the plate. The plate is provided along its sides and ends with a 

 series of screw-holes, to receive the milled head screws a of the 



clamps & d, by means of which the 

 knife e is made fast to the carrier, 

 and may be set at any desired 

 obliquity to the line of motion of 

 the carrier. The knife has a heavy 

 strong plano-concave blade with a 

 straight edge, and is laid flat upon 

 the carrier and securely clamped 

 down at heel and point. It, there- 

 fore, will not spring in the least 

 and may be depended on to do 

 work of very great precision. It is 

 used for cutting all kinds of wood 

 sections, and such other tissues as 

 can be cut by simply packing in 

 elder pith or imbedding in paraffin, 



Henking's Simple Microtome 

 Knife.* — Dr. H. Henking's knife 

 (figs. 72-74) has a short blade with 

 a bifid handle of the same length A. 

 The measurements of the blade 

 are: length about 5 cm,, breadth 

 about 28 mm,, thickness of back 

 about 7 mm. Though the back of 

 the blade and the handle are in 

 one and the same straight line, yet 

 the handle diverges from the plane of the blade so that the cutting 

 edge is 2^ mm. lower than the back B. The knife is supported by 



* ZeitscLr. f. Wiss. Mikr., ii. (1885) pp. 509-11 (1 fig.). 



