ZOOLOGY AND BOTANY, MICROSCOPY, ETC. 839 



pillars and against their arms, and this process is found so effective that 

 tissues of 6 in. diam. and upwards, and half an inch in thickness, are 

 frozen through in twenty minutes. Dr. Woodhead has made a further 

 improvement in the method of freezing by placing a shallow box filled 

 with a freezing mixture upon the plate. This box, the 

 under side of which is immediately over the tissue to be Fig. 154. 

 frozen, considerably accelerates the freezing process. 



The knife F is attached to a plate B, which slides in 

 grooves in the " plough " E E, and is moved forward or 

 backward by a screw. The capstan head is shown at G. 

 As the knife is placed obliquely, it moves but a small 

 distance vertically for each forward movement of the screw, 

 so that a comparatively coarse screw is as efficient as a fine one would 

 be if acting vertically. The plough is moved backwards and forwards 

 by two handles, one of which is shown at H, travelling in the rails at C C. 

 All the parts are made with " fitting strips," as in a slide-rest, so that 

 wear may be readily taken up. 



The dimensions of the apparatus are as follows: — Freezing-box, 

 length 22 in., breadth 12 in., depth 8 in. ; rails upon which the plough 

 slides, 34 in. long and 1^ in. wide; plough, 14 in. long and 8 in. high; 

 knife, 9 in. on cutting face. 



The microtome is made by Mr. A. Frazer, scientific instrument 

 maker, of Edinburgh. 



Thate's New Microtome.* — Herr P. Thate has invented an immer- 

 sion microtome which possesses ad^antnges in its arrangement of the 

 knife-carrier and circumvents certain difficulties inherent in the sliding 

 microtome. It is fully represented in fig. 155. 



The three columns Sj Sa Sg are connected near their base by a trian- 

 gular cast-iron piece. The pillar Si is hollowed out at the top, so that 

 the arm A, about 50 cm. long, may be worked through the ball-joint. 

 The columns S2 S3 are joined by the arciform piece B, along the uj)per 

 surface of which the end of the arm A, expanded at its extremity, works. 

 The expanded end of A is supported on two hard steel knobs. The 

 arm A is moved to and fro by the handle h. About 20 cm. from its 

 :free end the piece A is perforated by a slit through which the tap of the 

 binding-screw C projects, and by means of which the knife-carrier is 

 clamped to the arm A. For this purpose the lower end of C is swallow- 

 tiiiled, so that it may be pushed into a corresponding opening in the 

 double piece D, and that when the binding-screw is tightened it is fixed 

 to the arm A. The ends of D are gripped by the block E E, joined 

 together by a flat horizontal plate. To the under surface of E E the 

 ends of the knife are screwed, while through their upper extremities pass 

 the screws binding E E to D. Consequently, by altering the screws in 

 E E and the screw C, the knife can be placed in any desired position. 

 The amount of vertical movement of the edge of the knife, which, of 

 course, moves through part of a circle, is shown by the indicator at E. 

 F is the clamp for holding the specimen, and K the pan or well which 

 contains the fluid, water, or spirit. The clamp and well are formed in 

 one piece and fixed to the tube J, which in its turn passes through the 

 block G, and is fixed in any position by the binding-screw S. The 

 fine-adjustment of the block is effected by the micrometer-screw M, 



' Zeitschr. f. In.>trumciitenk., viii. (188S) pp. 176-7 (1 fig.)- 



3 L 2 



