CHAPTER XXXIX. 



THE SPINAL CAT (SHERRINGTON'S PREPARATION.) 



In this procedure the spinal axis is cut about 4 m.m. behind the 

 point of the calamus scriptorius, and the spinal animal exhibits a 

 considerable number of complex reflex movements, although the 

 arterial blood pressure remains low. Spontaneous respirations, of 

 course, cease entirely so that it is necessary to apply artificial 

 respiration. The control of body temperature also disappears, 

 necessitating artificial warmth. 



Demonstration 19. Anaesthetise a cat deeply, insert a 

 tracheal cannula low down and ligate the carotid arteries on both 

 sides of the neck. Place the animal in the prone position and 

 holding the head in the left hand, make a wide transverse incision 

 through the skin over the occiput and retract the skin downward 

 so as to expose the muscles of the upper end of the neck. Feel for 

 the transverse processes of the atlas and cut the muscles across at 

 the posterior edges of the processes. Cut off the spinous process 

 of the axis with a bone forceps. Thread a large packing needle 

 (at least 15 cm. long) with stout string, and pass it close under the 

 body of the axis (i.e., posterior to the cesophagus) and tie it tightly 

 in the depths of the cross cut. This ligature compresses the 

 vertebral arteries as they pass between the transverse processes of 

 the axis and atlas. 



The animal is now decapitated. For this purpose flex the head 

 so as to stretch the occipito-atloid membrane, and thrust the point 

 of a narrow (12 mm. wide) amputation knife through the membrane 

 moving it laterally so as to cut the cord. With the point of the 

 knife resting on the anterior wall of the spinal canal bend the head 

 forcibly to one side, and carry the edge of the knife through the 

 opposite occipito-atloid joint. Repeat this procedure for the other 

 joint and then complete the decapitation by cutting through the 

 remaining tissues. If there is bleeding it can be stopped by raising 

 the stump. When it has ceased, bring the skin flaps together over 

 the stump and lay the preparation on a warmed observation table. 

 Artificial respiration by means of a pump connected with the 

 tracheal cannula must of course be instituted before the cord is 



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