260 



SUMMARY OF CURRENT RESEARCHES RELATING TO 



The glycogen stains bright red, the nucleus pink and the cytoplasmic 

 framework pale yellow. Two disadvantages of the procedure are 

 mentioned, viz., the induration of the pieces and the superficiality of 

 the tanning. The tanning even of thin pieces is often limited to the 

 outer layers. In cutting the sections this must be borne in mind. 



Carbon-dioxide for Killing Marine Animals.* — A. G. Mayer fills a 

 siphon-bottle with sea-water and charges this with carbonic-acid gas by 

 means of the "sparklet-bulb." The charged sea-water is then poured 



into a vessel containing sea-water in 

 which the marine animals are living, 

 and in a few moments they are com- 

 pletely narcotised and may then be killed 

 in a fully expanded state by the addi- 

 tion of some fixative. In the case of 

 Siphonophorse the C0 2 should be fol- 

 lowed by the addition of a small quan- 

 tity of chloretone to prevent the swim- 

 ming-bells from being cast off. 



(3) Cutting - , including- Imbedding- 

 and Microtomes. 



New Freezing-stage for the Zim- 

 mermann Microtome.t — M. Wolff, 

 having been disappointed by the results 

 of freezing with liquid carbonic acid, 

 tried a spray of ethyl-chloride, and was 

 surprised beyond expectation with the 

 result. He experimented with a block 

 3 mm. high of Angioma freshly fixed in 

 10 p.c. formol with a section-plane of 

 p IG- 5 9 _ 2 cm. square. The freezing proceeded 



successfully in spite of the high tem- 

 perature (19° C.) of the room. He applied the block to a Zimmermann 

 microtome, and in one minute had cut so many sections (thickness 9 to 

 12 fx) that only 1 mm. of the block-height remained. The value of 

 the ethyl-chloride expended was only 15 pfenuige. This result en- 

 couraged the author to design a freezing-chamber specially adapted 

 for ethyl-chloride, and his design (fig. 59) was executed by the firm of 

 E. Zimmermann, Leipsic. His freezing-plate is, in contrast to the 

 plates of the paraffin-stage, provided with concentric grooves. It has 

 somewhat of the shape of a pill-box lid ; its underside faces the 

 interior of the apparatus, and is bored out cylindrically. The under- 

 side is covered with a coarse fibrous material for receiving the ethyl- 

 chloride which would otherwise drop off. This freezing-plate is now 

 screwed on a vulcanite ring connected with the usual stage carrying the 

 footpiece clamped into the object-holder. The vulcanite ring is pierced 

 with fifteen sufficiently large perforations through which the chloride 

 spray can, in every position of the chamber, be directed on to the 



* Biol. Bull., xvi. (1908) No. 1, December. 



t Zeitschr. wiss. Mikuosk., xxv. (1908) pp. 169-84 (4 figs.).'' 



