ZOOLOGY AND BOTANY, MICROSCOPY, ETC. 



91 



(3) Cutting, including' Imbedding- and Microtomes. 



Minot-Blake Microtome.* — F. Blake has devised a microtomo which 

 remedies the mechanical defects of its prototype the Minot Wheel- 

 Microtome. The substantial difference between the two instruments is 

 in the methods used for supporting and guiding those structural parts 

 by means of which the specimen to be cut is moved in a vertical and a 

 horizontal direction. The moving parts have only three bearing points, 

 and are held in contact with the guiding surfaces by the action of a flat 

 steel spring. The points which form the base of the triangle are V- 

 ehaped, and are held in contact with a V-shaped groove, while the third 



point is a flat block held in contact with a plane surface. The tripod 

 bearing insures absolute stability under contact ; and the stiff but 

 yielding bar-spring gives absolute contact and compensation for wear. 



From the description given by the Buff and Buff Manufacturing 

 Company the following further details are gathered. The microtome is 

 made up of a heavy base and fly-wheel of iron. The shaft and sliding 

 block are of hardened steel operating on hard composition metal, and 

 the vertical carriage moves on bell-metal uprights. The knife has a 

 blade of 1£ in. The feed-wheel is 7 in. in diameter, and is accurately 

 cut to 500 teeth. The micrometer feed-screw for the cross-feed has 

 50-8 threads to the inch (half millimetre pitch) so that a single tooth of 



* Jouru. Boston Soc. Med. Sciences, iii. (1893) pp. 75-S (3 pis.). 



