334 



RECOBD OF CURRENT RESEARCHES RELATING TO 



of the slides, the sides of which arc frequently not quite parallel. 

 The ends of the guides are cut and " sprung," so as to give sufficient 

 tension in the groove to obtain a firm grip of the slide. Guiding 

 lines and circles are ruled on the table to facilitate the centring, 

 and all that has to be done after placing the slide in position is to 

 bring the clips together by means of the pins until the requisite grip 

 is obtained. 



Further Improvements in the Rivet-Leiser Microtome.* — 

 Although this microtome is still superior in its chief points to pre- 

 vious instruments, particularly in the substitution of an inclined 

 plane for a screw, and in the guidance (controllable by the hand of 

 the operator) which is given to the knife, Dr. Spengel found that 

 further modifications were needed. A model used at the Zoological 

 Station at Naples (now some years old) has the advantage of allowing 

 increased thinness in the sections, which is accomplished by lengthen- 

 ing the instrument to 20 cm. instead of 10 cm., so that a movement 

 of ^ mm. of the object slide (the rise being 1 in 20) elevates the 

 object -^j^ mm. More recent attempts have resulted in the production 

 of an instrument shown in the annexed figures. 



Fig. 25. 



The first improvement consists of an arrangement for moving the 

 clamp, which holds the object, in two directions independently, the 

 object being capable in consequence of far more delicate adjustment 

 as regards its position than with an immovable clam]^ 



The clamp and object-carrier are shown in Fig. 25. By the 

 screw a passing through h (which is connected with d by two pins), the 



* 'Zodl. Anzeiger,' ii. (1S70) p. 641. 



