278 SIXTH RHl>ORT— 18.^6. 



gin, just where the larger and smaller flaps are about to conjoin, 

 receives one or two tendinous cords, which proceed directly from 

 the septum, without the intervention of any papillary muscle. 

 The smaller flap receives one or two of its tendons from the 

 lowest in position of those papillary muscles which have been 

 described as supplying the larger flap ; but all the others which 

 it receives, to the number of 12 or 14, proceed to it directly 

 from the surface of the septum, near the base, no papillary 

 muscle intervening^. 



From an inspection of the arrangement now described it is 

 manifest that the papillary muscles, when they contract, draw 

 the tendinous cords more or less towards the axis of the respect- 

 ive auriculo-ventricular openings ; and if it be supposed that 

 by any cause the flaps have been laid against the sides of the 

 ventricles, the contraction of the papillary muscles will remove 

 from such situation, or adduct towards the auriculo-ventri- 

 cular axis, those portions of the valves to which they are con- 

 nected. 



It is also clear that the contraction of the papillary muscles 

 cannot, in any instance, close the valves, or bring their flaps 

 into contact with each other. For when the contraction of the 

 papillary muscles is at its greatest, as at the end of the ventri- 

 cular systole, if it be assumed that the cords and flaps of the 

 valves have been rendered tense by their action, leaving al- 

 together out of view, for the present, the influence of the blood 

 upon the valves j and further, if it be supposed that the numerous 

 summits of papillae, whence the cords proceed, have been 

 gathered in each ventricle into a single point ; in such a state 

 of things each valve and its cords will have assumed a form 

 resembling an irregular funnel, of which the base is at the auri- 

 culo-ventricular opening, and the apex at the point of conjunc- 

 tion of the summits of the papillae : and it is evident that the 

 opposite points of the moveable edge of each valve will be sepa- 

 rated from each other by spaces equal to corresponding dia- 

 meters of the funnel. The assumption that the summits of the 

 papillae are congregated into a single point at the latter part of 

 the systole is manifestly incorrect, as the swelling of the papil- 

 lary muscles, during contraction, will tend rather to separate 

 from each other those summits which arise from the same pa- 

 pillary muscle 5 but in order that the edges of the valves should 

 be brought into contact by the action of the papillary muscles 

 alone, such an arrangement of those muscles would be necessary 

 as should cause the tendons of the opposing flaps to cross each 

 other during the systole, an effect totally incompatible with the 

 present construction of the organ under consideration. 



