CIRCULATION OF THE BLOOD. 



Examine the web of the foot on the same side as the cut nerve. 

 Stimulate the distal end of the cut nerve. What is the effect on the 

 capillary circulation ? Explain. 



Prepare another frog, cocainizing the sciatic nerve before cut- 

 ting. Compare the web circulation in this case, before and after 

 cutting, with the result obtained when the nerve was not cocainized. 



XXIV. RECORD OF THE BLOOD PRESSURE IN THE RABBIT. 



1. Preparation. Under the skin of the rabbit inject grain 

 of morphine sulphate. Anaesthetize lightly with ether. Expose 

 both carotid arteries, and isolate and identify the nerves running 

 with them. Pass two loops of thread about the vagus and de- 

 pressor nerves of each side. Introduce a cannula into the trachea. 

 Clean the carotid of one side for a distance of three or four centi- 

 metres. Pass two loops of thread around the artery. Tie the 

 upper ligature as far away from the heart as possible. Clamp the 

 artery near the lower part of its isolation. With a pair of fine- 

 pointed scissors make a V-shaped opening in the vessel near the 

 upper ligature, using the tied ligature to manipulate the artery. 

 Introduce a fine blunt-pointed seeker into the lumen of the cut 

 vessel toward the heart. Using this seeker as a guide, insert into 

 the artery a glass cannula made for the purpose. Tie this securely 

 in the vessel by means of the remaining untied ligature. 



In the mean time the apparatus for transmission and recording 

 of the blood pressure should have been made ready. This consists 

 of a revolving drum, covered with smoked glazed paper; a mer- 

 cury manometer with an upright and writing style resting on the 

 mercury of one limb of the manometer and arranged to write on 

 the drum; the other limb of the manometer is connected through 

 pressure tubing with the cannula which has been introduced into 

 the carotid. 



The proximal limb of the manometer, and the tubing connected 

 with it, are filled from a pressure bottle, with a half-saturated solu- 

 tion of sodium carbonate or some other salt solution to prevent 

 clotting of the blood which may find its way into the tubing. 



8 ["3] 



