GRAPHIC OF ARTERIAL PRESSURE 26 



leaving the noose drawn down to about 4 mm. diameter but untied ; tie the 

 two ends of (3) together in a knot close to their free tips. If thyroid branch 

 of carotid rises unusually low you may prefer to insert your arterial cannula 

 headward of it : in that case you must ligate the thyroid artery itself a little 

 way up its course, or you will have embarrassing haemorrhage when inserting 

 the cannula. 



Bring the free end of the junctional tube, with clamp l shut on it, the 

 clamp being about 2 cm. from its free end, close to the artery and conveniently 

 for picking up with left hand. Have arterial cannula and ' filler-up ' in a small 

 shallow dish of Ringer-Locke convenient for right hand. Open clamp e. Clamp 

 with artery-forceps the knot in ligature (3), and so place the forceps that under 

 its weight the thread drags on and occludes the carotid. With the left hand 

 pick up the free end of thread (1) and draw on it so as to straighten and steady 

 the piece of the carotid round which thread (2) lies as a noose. With the right 

 hand cut with fine sharp scissors a snip (PI. II, fig. 4) obliquely half through 

 the carotid about 4 mm. headward of the noose (2) ; exchange the scissors for the 

 glass cannula filled at its nozzle end with Ringer-Locke, and insert the nozzle 

 into the cut artery towards the heart so that the neck of the nozzle penetrates 

 as far as the place at which the noose lies. Leave go of the cannula gently 

 when it is thus engaged in the artery. Leave go gently of thread held in left 

 hand. Place tip of finger of left hand on the free end of the inserted cannula, 

 so as to keep it in place, and with thumb and forefinger of each hand tie the 

 noose tight round the neck of cannula and then complete and tie the reef- 

 knot. Fill the cannula completely with Ringer-Locke by the ' filler-up ', 

 seeing that no bubble of air is included in it. Take the end of the junctional 

 tube between the left thumb and forefinger at a point between free end and 

 the closed clamp and compress it closely. Loosen the clamp l partly with 

 right hand. Hold the cannula close below its free end firmly between right 

 thumb and forefinger, and with the left push the free end of the junctional 

 tube over that of the cannula, relaxing the compression of the tube somewhat 

 in doing so, thus allowing the fluid to overflow from the end of the junctional 

 tube and run into and overflow that of cannula as well. A fluid junction 

 free from all air-bubbles is thus obtained. Close clamp e. Then at once 

 relax the compression of the proximal point of the carotid by thread (3). 

 Open freely the clamp l on junctional tubing. Observe the movement of the 

 Hg in the manometer and of the manometer float. Arrange the junctional 

 tube in such a way that the artery is not too curved or stretched, and leave it 

 in some position in which the movements of the Hg are full and free. The 

 junctional tube must rest adjusted to suit the artery, and usually requires some 

 support. Swab up the fluid that escaped from the junctional tube into the 



