537 



On the Mechanism of the Cardiac Valves : a Preliminary 

 Communication. 



By A. F. Stanley Kent, M.A. Oxon., Henry Overton Wills Professor of 

 Physiology in the University of Bristol. 



(Communicated by Prof. C. S. Sherrington, F.R.S. Received February 15, 1915.) 

 (From the Physiological Laboratory of the University of Bristol.) 

 [Plate 16.] 



The account commonly accepted of the manner in which the auriculo- 

 ventricular valves of the mammalian heart are operated relies chiefly upon 

 the action of eddies and currents. As the result of recent work it appears 

 possible that a muscular mechanism may be involved also. Such a mechanism 

 is referred to in the following communication. 



It consists of a prolongation downwards of the muscular fibres of the 

 auricular wall in such a manner as to produce a sheet of longitudinally 

 coursing fibres which enter the base of the valve flaps and run a variable 

 distance in their auricular portions.* 



The general arrangement may best be gathered from the accompanying 

 photographs. These, wbich have been taken from sections of the hearts of 

 different animals, show that muscular fibres, originating in the auricular 

 wall, sweep down to the valve flaps, which they enter, and become inserted 

 into the connective tissue at some distance from the base. 



The passage of this muscle from auricle to valve is uninterrupted, and the 

 tissue found in the valve is similar histologically to that found in the auricle. 

 Moreover, the muscle is present in considerable amount, and may even form 

 the greater part of the thickness of the valve. It is particularly to be noted 

 that the muscular tissue described as running into the valve arises from and 

 is continuous with the muscular wall of the auricle. 



A reference to the figures will show that in fig. 1, which is taken from 

 a section of the heart of a three weeks old rat, the muscular fibres of the 

 auricle pass without structural change down to the auriculo-ventricular 

 junction, where they come into close relation with the ventricular tissues. 

 In the neighbourhood of the mass of connective tissue from which the valve 

 springs the muscle fibres become arranged parallel to the axis of the valve 



* I would point out that the muscle described in this paper should not be confused 

 with the interesting sphincter of unstriped muscle, the existence of which at the 

 A-V orifice is mentioned by 1 Prof. Gustav Mann in the last edition of Quain's 

 ' Anatomy.' 



