PRACTICAL EXERCISES 99$ 



The operator, standing on the left side of the animal, applies the mid- 

 point of the sharp edge of the blade, bevelled side forward, to the 

 point notched in the interparietal ridge, the width of the blade being 

 kept truly at right angles to the median plane of the head. The knife 

 thus held in the left hand is kept vertical, or nearly so, and is directed 

 so that the plane of the blade if continued downward through the 



Fig. 401. Cat Decerebrator (Miller and Sherrington). N, wooden neck- block, 

 mounted firmly on a strong base-board. N is inclined at 22 to the vertical 

 and supported by two stout wooden props meeting it somewhat below its top 

 at an angle of 44. The top edge of the neck-block (cut at right angles to the 

 face of the block) is therefore at an angle of 22 to the horizontal. Y, yoke, a 

 Y-shaped fork of wood with one of the prongs projecting 6 centimetres beyond 

 the top of the neck-block, the other prong truncated nearly to its base. A 

 Y-shaped steel plate (the yoke-plate) is screwed to Y. It is shaped somewhat 

 like the wooden yoke, but its two side prongs are of equal length, and between 

 them projects a shorter prong, T, the tongue-guard. S is a T-shaped wooden 

 nose-piece, adjustably attached to the front of the steel-covered yoke. In the 

 upper border of the cross-piece of the T, is a V-shaped notch. A slot in the stem 

 of the T allows the T-block to be slid up or down on the steel yoke-plate, and 

 it can be fixed at any position by a thumb-screw. C, a leather cord passing 

 through a hole piercing neck-block, yoke and yoke-plate. The top end of the 

 cord, issuing from the hole in the mid-line of the yoke-plate, carries a short 

 Strong hook. The point of the notch in the nose-piece slides up to and slightly 

 beyond this hole. P, a light single-pillared platform, somewhat saddle-shaped 

 at the top, which can be slid on the baseboard nearer to or farther from the 

 neck-block. 



head would meet a horizontal line engraved on the side-prongs of the 

 yoke-plate. This line is at the level of the free end of the tongue- 

 guard. A light blow is then struck with a mallet on the top of the 

 handle of the knife, sufficient to engage the edge in the skull in the 

 proper direction i.e., toward the horizontal line on the metal plate. 

 Then with a couple of heavier blows the head is severed in the desired 

 plane. 



