954 SUMMAEY OP CUREENT RESEARCHES RELATING TO 



bath to the temperature of the melting-point of the paraffin used, and 

 allowed to cool. The creosote is then evaporated, and the section 

 fixed so well by the shellac that turpentine can be let pass over it 

 freely without displacing it. After covering with Canada balsam, 

 the shellac-layer is no longer discernible, provided it was thin and 

 uniform. 



Imbedding in Paraffin.* — Mr. E. L. Cheeseman, iu cutting 

 vegetable sections, makes a short paper tube the same size as the 

 well-hole of the section cutter, by rolling a strip of paper round a 

 cylinder ; a cork is fitted to one end of the tube, and to the upper 

 side of the cork is attached by cement or otherwise the specimen 

 to be cut (previously hardened in alcohol, if necessary) in such a 

 manner that it will stand upright in the centre of the tube. Fill the 

 tube with melted paraffin, and when cold remove the paper, and there 

 is a i)lug of paraffin enclosing the specimen. Several of these plugs 

 should be made at a time, and kept in alcohol until wanted. 



Taylor's Freezing Microtome. — At the last meeting of the 

 American Association for the Advancement of Science, Mr. Thomas 

 Taylor, Microscopist of the Department of Agriculture at Washington, 

 presented a model of a new freezing microtome of his invention, 

 which consists of a thin brass tube about 1^ inch in length, by 

 1 inch in diameter, with a ^-inch brass tube secured within the larger 

 cylinder. This tube enters the bottom where it is secured, and pro- 

 ceeds to within a quarter of an inch of the inside surface of the top. 

 To the outside open end of this tube a rubber tube is attached ; the 

 other end of the rubber tube is made to communicate with a freezing 

 mixtm-e composed of finely cut ice and salt in about equal proportions. 

 The pail containing this mixture is placed over and about 15 inches 

 higher than, the section-cutter. The object of this arrangement is to 

 fill the brass cylinder with a freezing liquid, drained from the pail, 

 and produced by the liquefying salt and ice, the temperature of which 

 is about zero. On filling the cylinder with the liquid any object on the 

 top of the cylinder becomes frozen in a short time, and may then be 

 cut to any degree of thickness. In order to preserve the low degree 

 of temperature in the cylinder, a second tube is secured in the cylinder 

 to remove air and to keep up a constant current of the freezing liquid. 

 This tube also enters the bottom of the cylinder, where it is fastened. 

 It projects upward to within an eighth of an inch of the top, and has a 

 diameter of about one-half of the supply tube. This microtome in 

 other respects is arranged like the ordinary microtomes, used for ether 

 or rhigoline. 



Waller's Section-knife for large Sections.f — Dr. B. C. Waller 

 recommends a knife, for service chiefly with the larger freezing micro- 

 tomes, with wells 2 inches in diameter, and in making large sections. 

 It consists (Fig. 226) of a blade 7i inches long, 2 inches broad, and 

 ■{^^ of an inch in thickness at the back, set at right angles upon a stout 



* Amer. Mon. Micr. Journ., ii. (1881) p. 114. 

 t Ediuburgli Med. Journ., xxiv. pp. 893-5. 



