54 



EXEECISE VIII 



Obs. 36. 

 Aortic stenosis 

 on art. pressure 

 and pulse. 



Obs. 37. 

 Aortic insufla- 

 ciency on art. 

 pressure 

 and pulse. 



loop, the far ends of the thread being knotted together so that a clip will grip 

 the knot without slipping. Cut open the pericardium at its upper part 

 (PI. II, fig. 6) and expose the ascending aorta down towards the heart ; it is 

 partly covered by fatty tissue attached to it. The right auricular appendix 

 partly overlaps its root ; the pulmonary artery springs from in front and passes 

 up to the left of it. 



IV. Note the large artery springing from the aortic arch to the left beyond 

 the origin of the innominata ; this is the left subclavian. The opening you 

 have made in the chest exposes the left subclavian for a long portion of its 

 length, as it slopes neckwards and towards the left to emerge from the chest 

 and enter the axilla. A relatively small branch springs from it before it 

 emerges from the chest ; this is the left internal mammary. Free the upper part 

 of subclavian from tissue and ligate it close below the internal mammary. Then 

 below this ligature place two others, the upper to secure the cannula you are going 

 to insert, the lower a loop to occlude the artery during insertion of the cannula. 

 Insert the cannula towards the heart with the precautions for blood-pressure 

 records (exerc. V) ; connect with the membrane-manometer tube, taking 

 care to avoid air just as in previous exercises with the Hg. manometer. 

 Eecord a sample of the subclavian pressure with the kymograph, and take 

 pains to place the connecting-tube so that the pulsations are as free as possible 

 and the tube fixed so as to secure that. 



[V. Return to the exposed root of the aorta, and carefully separate it 

 somewhat from pulmonary artery and auricle. With blunt curved needle 

 pass a thick thread round the aorta root, introducing the thread from the 

 animal's left side. Tie loosely the first bend of a reef-knot and leave the 

 thread-ends loose for pulling upon. 



Start kymograph, and after a few seconds draw on the thread noose 

 round aortic root, partly occluding the vessel. Observe effect on the arterial 

 graphic. Release the drag on the thread. Then carefully tighten somewhat 

 the tie of the thread, so as to constrict but not occlude the vessel. Note 

 effect on the kymograph record. Then remove the thread altogether.] 



VI. Oil the end of the wire stylets for rupturing the aoi*tic valve and 

 lay them ready for use. Choose for this the largest stylet you think you can 

 insert. Return to the innominate artery. Tie (PI. II, fig. 6) the thread (1). 

 Attach a weight to the thread (8) and arrange the weighted thread so that it 

 occludes the innominate completely close to its origin from aorta. Set the 

 kymograph record running. Note that the pulse oscillations are, relatively to 

 the mean pressure, much larger than in your records taken with the Hg 



