ELEMENTARY DEMONSTRATIONS 



129 



The carotid artery is 



a rabbit is anaesthetised with urethane. 

 exposed, and a canrmla inserted. The 

 cannula is connected to a mercurial 

 manometer by a piece of pressure 

 tubing, a J_ piece being interposed. 

 The cannula and tube are filled by 

 means of a pressure bottle or syringe 

 with sodium citrate 1 per cent, 

 solution, and the pressure in the 

 manometer is raised to about the 

 arterial pressure. The vagus nerve is 

 exposed, ligatured in two places, and 

 divided between the ligatures. The 

 depressor nerve is exposed, ligatured, 

 and divided below the ligature. The 

 depressor in the cat runs separately 

 from the vagus on the left side. On 

 the right side it can generally be 

 separated from the rest of the vagus 

 without much difficulty. In the rabbit 

 the depressor runs separately on both 

 sides. In the dog it is bound up in the 

 vago-sympathetic trunk. 



The trachea is opened and a tracheal 

 cannula inserted. This is connected 

 with the anaesthetic bottle and by a 

 side tube with a recording tambour. 

 The writing styles of the manometer 

 float and of the tambour are brought 

 to write on the kymograph exactly 

 beneath one another. A clock marking 



. . FIG. 105. Mercurial manometer fitted 



seconds and an electric signal placed in with float and writing style. 



the primary circuit are also brought to write on the kymograph. The 



FIG. 106. Recording tambour. 



primary circuit is arranged to give tetanising shocks, and shielded 

 electrodes are connected with the secondary coil by means of a Du Bois 



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