ZOOLOGY AND BOTANY, MICROSCOPY, ETC. 377 



A two-armed lever d e is secured to the underside of the slide, and to 

 one end of the lever the roller is applied ; on the other end (fig. 90) 

 acts, by means of a bolt /, a strong spiral spring g, which can be 

 tightened or relaxed by a screw (h, figs. 90 and 91). Screw, spring, 

 and bolt lie in a perforated canal in the lower massive part of the slide. 

 When the spring is tightened by the screw, the roller can therefore be 

 raised and pressed as tightly as desired against the bar. The effect is 

 to totally deprive the slide of anything like loose play. The spring 

 pressure can obviously be varied at pleasure, and the slide can therefore 

 be regulated as circumstances require. A secondary result is an in- 

 creased pressure on the micrometer screw, which has therefore needed 

 some strengthening. This slide-brake can be applied to existing 

 microtomes of the Jung type. 



Apparatus for Imbedding in Paraffin.* — Dr. P. Meissner describes 

 a useful apparatus for imbedding objects in paraffin. It consists of a 

 tank made of copper with a well sunk in at the top. The well is for 

 the reception of a rectangular bath, and into the latter fits a wire cage 

 in which the paper moulds are placed. Level with the bottom of the 

 well is a pipe which connects by means of rubber tubing with a tank 

 containing cold water. After the specimens have been satisfactorily 

 oriented the paraffin is made to set by letting the cold water flow into 

 the well. This device prevents the formation of air-bubbles. The 

 pan or paraffin bath is then lifted out of the well and hung up outside 

 the bath on the arms of two supports fixed to the top of the tank until 

 the paraffin is completely set. 



Rapid Method of making Permanent Preparations of Frozen Sec- 

 tions. | — J. H. Wright makes preparations fully equal to paraffin or 

 celloidin sections by the following procedure : — A piece of tissue not 

 exceeding 5 mm. in thickness is placed for 2 hours or more in 10 p.c. 

 formalin, or may be boiled therein for 2 or 3 minutes. The sections 

 made with a freezing microtome are floated on to a slide, and after the 

 superfluous water has been run off are covered with a piece of cigarette 

 paper. On this is placed a pad of filter paper, moistened with 95 p.c. 

 alcohol, and after pressure has been applied the pad and cigarette paper 

 are removed. The section is then flooded with absolute alcohol, and 

 after this has been drained off a very thin solution of celloidin is 

 allowed to run over the surface of the section to adjacent parts of the 

 slide. After draining off any superfluous celloidin solution, the slide 

 is flooded with 95 p.c. alcohol, and then at once plunged in water for 

 10 seconds. The section may now be stained by any method. It is 

 then dehydrated in 95 p.c. alcohol, followed by a little absolute alcohol, 

 after which it is cleared with oil of origanum and mounted in balsam. 

 Alcohol or Zenker's fluid may be used for fixing instead of formalin, 

 but then the piece of tissue must be thoroughly washed in water to 

 remove the fixative. 



This method not only prevents distortion of the section by de- 

 hydrating and clearing agents, but it also saves much time, and a dia- 

 gnosis may be made within a few minutes after the specimen is received. 



* Zeitschr. wise. Mikr., xviii. (1902) pp. 2S6-8 (1 fig.). 



f Mallory and Wright, Pathological Technique, Philadelphia, 1901, p. 417. See 

 Journ. App. Microscopy, v. (1902) pp. 1670-1. 



