ZOOLOGY AND BOTANY, MICEOSCOPY, ETC. 



347 



shorter one, having a fine screw-thread terminating in r. The clamp- 

 screw d fixes it. A ring / with a screw-thread works in that on the 

 short cylinder, its upper edge serving as a guide for the knife. By 

 rotating the ring it is lowered and more of the object to be cut exposed 

 to the knife. The divisions on the ring mark 1/10 mm. in the thick- 

 ness of the sections. 



Reichert's Microtome Object-clamp. — C. Eeichert now supplies 

 for use with his microtomes the clamp shown in figs. 87 and 88. The 

 object is fixed between two plates, one of which is movable and is 



Fig. 87. 



Fig. 88. 



controlled by the screw on the left. A universal motion is given to 

 the clamp by a ball-and-socket arrangement shown in section in 

 fig. 88, so that it can be set at all inclinations. 



Improvements in Microtomes and Knives.* — P. Francotte sug- 

 gests attaching to the plate of the Eanvier microtome, on each side of 

 the opening, two pieces of glass, • 5 cm. broad, and of exactly equal 

 thickness. These will serve as slides for the razor, which, owing to 

 the reduction of friction, will move more regularly, and thus perfectly 

 parallel sections will be obtained which it is otherwise difficult to do. 



Another suggestion is to attach two pieces of glass, 1 mm. thick, 

 to the plane face of the razor, a little less in length than the breadth 

 of the blade, so as to leave the edge free. The glass would be better 

 replaced by metal, but that would require a specially constructed 

 knife which it is the object of his suggestions to avoid. 



Rogers' Section-Cutter.f — W. A. Eogers describes a form of 

 section-cutter suggested by part of the mechanism employed in the 

 comparator of Princeton College. New tree-ways upon which the 

 Microscope-plate moves are the cores of very long magnets, and it was 

 found that the pulling force required to move the plate under the 

 action of a current developed by four bichromate cells was about 

 135 lbs. 



The apparatus now proposed obviates the uncertainty as to the 

 mechanical indication of the thickness of the sections as well as the 

 uncertainty with reference to its rigidity and the number of parts by 



* Bull. Soc. Belg. Micr., xi. (1885) pp. 84-5. 



t Proc. Amer. Soc. Micr , 7th Ann. Meeting, 1884, pp. 191-3. 



