ZOOLOGY AND BOTANY, MICROSCOPY, -ETC. 363 



Orientation of the Embryo.* — It is often necessary, in dealing 

 with very young embryos, to carry out fixing and hardening processes 

 upon the entire Graafian follicle. This prevents undue risk of injury 

 to the embryo, but has the disadvantage that the membrane becomes 

 opaque, and it is then impossible to ascertain the exact lie of the con- 

 tained embryo. Thus, if it be desired to cut serial sections of the whole 

 structure in any particular plane, some means of determining the orien- 

 tation of the embryo is necessary. 0. Zajicek, working upon mole 

 embryos, removes a Graafian follicle, together with part of the uterus. 

 In order to facilitate access of the fixing fluid the uterine muscle is 

 gently stretched. After fixing in Zenker's fluid, the preparation is 

 passed through rising alcohols, and then put into aniline oil. In this 

 reagent the follicular membrane becomes transparent, and the exact 

 position of the embryo may be observed. With a fine pair of forceps 

 a small window, indicating the position of the head, may be cut, so that 

 the orientation remains ol)vious during the subsequent embedding 

 process, in which the follicle-wall again becomes opaque. 



(3) Cutting:, including- Embedding: and Microtomes. 



New Rotary Microtome. f — H. N. Ott gives a description of the 

 Spencer Microtome, a new type of instrument, which possesses certain 

 advantages over older patterns of rotary microtome. The importance 

 of securing a satisfactory rotary microtome for laboratory workers who 

 are embedding in paraffin and embedding in serial sections is great. 

 The construction of this instrument is very solid and rigid. The whole 

 of the feeding mechanism is covered, thus protecting the wearing parts 

 from dust. AVhen it is necessary to get at the working parts the hinged 

 cover may be thrown back. The block which carries the specimen 

 moves up and down upon the support, while the object-clamp moves 

 freely backwards and forwards upon the block. By this combination 

 the difficulty of fitting a block capable of moving in all these directions, 

 without any chance of lateral displacement, is obviated. Full details 

 of the mechanism are given. 



t)' 



Classification of Injection Methods. J — B. Mozejko gives a detailed 

 classification of the various methods for obtaining injected preparations 

 of animal tissues. These fall generally into three classes — the inter- 

 stitial and intravital methods and those described as " Selbstinjektionen." 

 The author discusses at length the intravital methods, giving an historical 

 resume of different procedures that have been employed, and deals also 

 with the types of material that have been found suitable for injection. 

 Tissues are said to undergo self -injection when, upon treatment with a 

 chemical substance which possesses affinities with certain constituents 

 of the tissues, a demonstrable differentiation of specific cells or systems 

 is produced as a consequence of the treatment. 



* Zeitschr. wiss. Mikrosk., xxviii. (1912) pp. 424-6. 



t Zeitschr. wiss. ^Mikroak., xxviii. (1912) pp. 451-5 (fig. 1, p. 452). 



X Zeitschr. wiss. Mikrosk., xxviii, (1912) pp. 432-44. 



2 c 2 



