144 



IN THE FRONT PERSPECTIVE THE POINT 

 OFTHE PYRAMID /S PLACED EXACTLY 

 AT RIGHT ANGLES TO THE ED&E OF 

 THE HNIFE. 





OBJECT-NOLDER 



PLAST/C PYRAMID 



KNIFE 



-^ 



TROUGH 



F'is. 263. Pyramid and trough, front view. 



By hand, and with the motor off, the pyramid is brought to the level 

 of the knife. In order to prevent damage to the pyramid through the 

 vertical movement of the microtome, the trough with the knife should be 

 placed at a safe distance. The knife is then slowly brought forward to the 

 apex of the pyramid. 



Fig. 261 outlines the mobile part of the microtome, the knife-trough part 

 (side view), and the vertical adjustment of the lever of the microtome with 

 the mounted plastic unit. Fig. 262 shows the knife-trough block and the 

 microscope. 



The final adjusting for sectioning is followed under the microscope. In 

 the visual field will be seen the facet of the knife, the liquid (20 per cent 

 alcohol in water) with which the trough has been filled, and the plastic 

 unit with a part of its holder. One of the base lines of the pyramid must 

 be parallel to the facet of the knife which should be brought as near as 

 possible to the apex of the pyramid without coming into contact with it. 

 The knife-trough block is then fixed, and the level of the liquid checked 

 (the surface should be slightly convex). 



The motor is then started. Some introductory movements of the micro- 

 tome carry the apex of the pyramid towards the knife. The microtome 

 feeds at every second stroke. Normally, the sections assemble in the 



