180 DR D. NOEL PATON ON THE 



of the action of the valves. The same objection applies to the more recent experiments 

 of Sandborg and Worm-Muller. (Pfluger's Arch., Bd. 22, S. 108.) 



Third. The experimental observations of Chauveau and Faivre (Gaz. Med., 1856) 

 on the heart of the horse during life have by many been accepted as strongly supporting 

 this view. These investigators state that if the finger be introduced into the right 

 auricle so as to palpate the valve, one feels at the moment of ventricular systole " les 

 valvules triglochines se redresser, s'affronter par leurs bords, et se tendre au point de 

 devenir convexes par en haut, de maniere a former un dome multiconcave audessus de 

 la cavite ventriculaire." They made no experiments on the mitral valve. 



When, however, we come to examine this generally accepted view, several serious 

 objections at once present themselves. 



First. The value of Chauveau and Faivre's observation is considerably diminished 

 by the fact that subsequent observers have not confirmed it. 



Ktiss (Cours de Physiologie, 1872, p. 149) says, after giving the usual description 

 of the closure of the valves, "Mais le fonctionnement est tout autre, car en introduisant 

 le doigt vers le region auriculo-ventriculaire, au moment de la systole ventriculaire, on 

 voit que l'espece d'entonnoir qui pend de l'oreillette dans le ventricule continue a 

 exister." 



Second. It is impossible that the valves should be closed in the manner described. 

 When the ventricle is fully distended, the chordae tendinese are stretched between the 

 valves and the papillary muscles, as was clearly described in 1880 by Hesse (Arch. f. 

 Anat. u. Phys., 1880, p. 346) ; and unless the first change in ventricular systole is a 

 very marked shortening of the ventricular cavity, it would be impossible for the cusps of 

 the valves to be raised into the horizontal position described, even if the papillary 

 muscles did not, from the first, participate in the contraction of the walls of the chamber. 

 Now Hesse has clearly shown that even in the third stage of ventricular systole the 

 apices of the papillary muscles are only very slightly approximated to the auriculo- 

 ventricular orifice. 



Third. If the valves are closed as usually described, a large part of the mass of blood 

 which is lying between the cusps must be forced back into the auricles, and thus a 

 considerable regurgitation must occur. 



Fourth. The horizontal septum between auricle and ventricle formed by the elevated 

 valves is composed of a comparatively thin membrane. When the auricle relaxes, as 

 ventricular contraction goes on, this membrane must be subjected to a sudden and 

 enormous pressure, amounting in the left ventricle to about 3450 grms., and in the 

 right to 1664 grms. (Onimus, Journal de VAnatomie, 1865, p. 351), which its structure 

 is not specially adapted to withstand, and which certainly one must, a priori, anticipate 

 would tell prejudicially upon such living membranes. In short, the mechanism as usually 

 described is a bad one. 



Fifth. It appears strange that such well-developed structures as the papillary muscles 

 should play so small a part in the action of the structures into which they are inserted. 



