

THE EVENTS OF THE HUMAN CARDIAC CYCLE 85 



Riegel ( 4l ), and Francois-Franck (). In 1893-4 Mackenzie (*) 

 published his first papers, which, with his collected observations on 

 14 The Study of the Pulse," appearing in 1902, have given the 

 impetus to a careful investigation of the whole subject. 



Pulsation in the veins of animals is not confined to the larger 

 vessels feeding the auricles ; it is a constant phenomenon in dogs, 

 cats, and rabbits, and may be seen extending in many of them 

 into the smaller veins of the neck and limbs. Gottwalt was of 

 opinion that the jugular veins of all normal persons pulsate., and 

 this conception is receiving constant confirmation. It is possible 

 at the present time to obtain venous records from the neck of a 

 large percentage of normal individuals ; Wenchebach states that 

 it is feasible in most subjects, healthy or diseased. Pulsation is 

 frequently so well marked as to be visible, and in thin or anaemic 

 subjects often constitutes an obvious movement. It is highly 

 probable that with improved apparatus curves will be invariably 

 obtainable. 1 Any agency which tends to promote a heightened 

 venous pressure, such as raised intra -thoracic or abdominal pres- 

 sure, or gravitation, increases the force and visibility of venous 

 pulsation. It is for this reason that tracings are best taken 

 in the reclining posture, and that in those cases, where pulsation 

 is feeble, expiratory suspension of respiration increases its 

 prominence. 



In man, the venous pulse is seen and recorded with the greatest 

 facility in those veins which have but a short distance to travel 

 before reaching the heart. A special and valuable anatomical 

 description of the veins ot the neck in relation to this subject has 

 recently been given by Keith ( 28 ). Tracings may be taken direct 

 from the external jugular vein when this is engorged, but more 

 often the receiving instrument must be applied to the jugular 

 bulb, which lies a little above and 25 mm. external to the sternal 

 end of the clavicle. 2 A needle passed back into the neck at this 

 point strikes the internal jugular vein at a point where it is 

 guarded by a pair of valves, which, when the path to the auricle 

 is obstructed, or when blood is regurgitated, produces a bulging 

 in the vessel from which the " bulb " derives its name. Passed 

 further on the needle transfixes the subclavian artery. Tracings 



1 If they are not already. 



1 The receiver should be as a rule aii>lir<] K-twrru the two heads of origin of 

 the stcrno-mastoid muscle. 



