ZOOLOGY AND BOTANY, MICROSCOPY, ETC. 553 



are usually cut ; but at least one point can be indicated with consider- 

 able accuracy. Small sections can always be made to chain when cut 

 from a good paraffin of 45° 0. melting-point in a room in which the 

 thermometer stands at 16° to 17° C (The temperatures quoted 

 apply to the case of rooms heated by an open fire, and probably would 

 not apply to the case of rooms heated by closed stoves, such as are 

 usual in Germany.) At 15° C. the paraffin will be found a trifle 

 hard. At 22° C, the proper melting-point of the paraffin will pro- 

 bably be found at about 48° C. Second, the knife should be set 

 square. Third, the block of paraffin should be pared down very close 

 to the object, and should be cut so as to present a straight edge parallel 

 to the knife-edge ; and the opposite edge should also be parallel to 

 this. The block should in no case be cut so as to present a pointed 

 side, as recommended at the Naples Zoological Station.* Fourth, 

 the sections ought to be cut rapidly, with the swiftest strokes that 

 can be produced. It is evident that this condition can only be conve- 

 niently realized by means of a sliding microtome; but it is by no 

 means necessary to have recourse to special mechanical contrivances, 

 as in Caldwell's automatic microtome. The Thoma microtome, well 

 flooded with oil, is sufficient. 



Rapid Method of making Sections of hard Organized Substances.! 

 — Dr. F. V. Hohnel first files the object (e. g. a piece of hard wood) 

 level with an ordinary file, and makes the surface quite even with 

 finer files. A piece (1/2-1 mm. thick) is then split off with a scalpel 

 or cut with a saw from that portion which has been filed smooth. A 

 drop of Canada balsam is then placed on a slide, and on it the piece 

 of wood, with the filed surface below, and the slide warmed till the 

 balsam is melted. The wood is then pressed down firmly with the 

 finger, and the slide set on a cold metal plate till the balsam is 

 cold, a small piece of blotting-paper being laid on the object, which 

 is pressed firmly on the slide with a soft cork. The blotting-paper 

 and superfluous balsam are then removed. The section is next filed, 

 till it is so thin as to be transparent, with a coarse file, and with finer 

 files until it is quite smooth and shining. If the section is to be quite 

 faultless it is rubbed for a short time on a dry Mississippi or Arkansas 

 stone, which should be freed from adherent particles of resin with a 

 cloth damped wdth alcohol. After the final filing and polishing the 

 slide and edge of the object are cleaned with a towel wetted with 

 alcohol. The object is then mounted in Canada balsam or glycerin. 

 In this way ten to twelve sections can be prepared in a day. 



Contribution to the History of Staining. J — Prof. G. Holzner 

 writes to claim that G. C. Eeichel, of Leipzig, was the originator of 

 the process of staining for histological purposes. In his ' De vasis 

 plantarum spiralibus,' 1758, he not only pointed out the different 

 behaviour of the tissues and their elements with a decoction of log- 

 wood, but used the reagent for the discovery of the vessels. 



* See this Journal, ili. (1883) p. 917. 



t Zeitscbr. f. Wiss. Mikr., i. (1884) pp. 231-5. 



% Ibid., pp. 254-G, 



