ZOOLOGY AND BOTANY, MICROSCOPY, ETC. 104:7 



the fluid but vapour of superosmic acid, the alga to be hardened being 

 placed in a hanging drop on a glass slide over the mouth of the flask 

 containing the osmic acid. But this plan answers only when the object 

 to be preserved occurs in the drop in considerable quantities. When it 

 is solitary, or present only in very small numbers, the water in which it 

 is contained must be partially evaporated in a watch-glass, a watch-glass 

 containing from 5-10 drops of osmic acid being also placed in the 

 evaporating-chamber ; after the drops of the fluid have been partially 

 evaporated dilute glycerin is added. 



Glycerin-jelly is especially valuable as an imbedding material for 

 such objects as are difficult to inclose in glycerin in consequence of their 

 slipperiness. 



Simple Method for Fixing Cover-glass Preparations.* — Dr. M. 



Nikiforow fixes fluids, e. g. blood, on cover-glasses by immersing them 

 for one or two hours in a mixture of ether and absolute alcohol. TIjb 

 cover-glass is then taken out, and having been dried in the air, is 

 stained by Ehrlich's method. 



The process may also be used when micro-organisms are to be 

 stained. 



Klein, L. — Beitrage zur Teelmik der Mikroskopischen Dauerpraparate. (Contri- 

 butions to tha technique of microscopical permanent preparations.) 



MT. Bot. Vercins Freiburg, 1888, Nos. 49 and 50, 7 pp. 

 Lamb, D. S. — Notes on the Technique of Frozen Anatomical Sections. 



Amer. Mon. Micr. Journ., IX. (1888) p. 205. 



C3) Cutting-, including- Imbedding-. 



Cathcart Improved Microtome. — This instrument (fig. 182) differs 

 from the original Cathcart Microtome in the following points : — (1) The 

 principal screw is of larger diameter than in the old form, and has a head 

 of considerably greater size ; (2) The wooden frame is made with a pro- 

 jecting part, by means of which the instrument may be clamped on hoth 

 sides, and two clamps are supplied ; (3) The freezing-plate is made of 

 circular sha])e, is supported on three pillars, and is provided with a 

 ledge to prevent the ether getting to the upper side of the plate ; (4) 

 The construction of the instrument has been so modified that it may 

 be used both for specimens frozen in gum and those imbedded in 

 parafl&n or celloidin. 



The increased size of the screw gives a more steady movement than 

 was possessed by the older and smaller microtome, while the greater 

 circumference of the screw-head enables the operator to impart a finer 

 movement to the screw. The relation between the pitch of the screw 

 and the circumference of its head is such, that if the edge be moved 

 forward a quarter of an inch, an object will be raised one-thousandth 

 of an inch ; and if it be moved an eighth of an inch, the object will be 

 raised the two-thousandth of an inch. 



It is found that, when the instrument is clamped at both sides less 

 pressure need be applied at either side; and the tendency which the 

 instrument had to turn upon the point of clamping, as on a pivot, is quite 

 done away with. 



In the original instrument, the plate was supported on two pillars 

 in order that as little heat as possible might be conveyed to the freezing- 



* Zeitschr. f. Wiss. Mikr., v. (1888) p. 340. 



