[ . 207 ] 

 XXVI. Proceedings of Learned Societies, 



ROYAL SOCIETY. 



1835. npHE reading of a paper, entitled, " On the Influence of 

 June 4. — A the Tricuspid Valve of the Heart on the Circulation 

 of the Blood." By T. W. King, Esq,, M.R.C.S. Communicated by 

 Thomas Bell, Esq., F.R.S., — was resumed and concluded. 



The purport of this paper is to prove experimentally that the tri- 

 cuspid valve of the human heart does not, in the ordinary state of the 

 circulation, completely prevent the reflux of blood from the ventricle 

 into the auricle on the right side, and that the amount of regurgita- 

 tion is continually varying according to the different degrees of disten- 

 tion of the ventricle. The author points out the anatomical differences 

 between the auriculo-ventricular valves on the right and left sides of 

 the heart; from the consideration of which it might have been inferred, 

 independently of direct experiment, that while the structure of the 

 mitral valve is adapted to close accurately all communication between 

 the left auricle and ventricle during the contraction of the latter, that 

 of the tricuspid valve is designedly calculated to allow, when closed, 

 of the flow of a certain quantity of blood from the right ventricle back 

 again into the auricle. The comparatively imperfect valvular func- 

 tion of these latter membranes is shown by various experiments on 

 recent hearts, in which it was found that while fluids injected into 

 the left ventricle, through the aorta, were perfectly retained in that 

 cavity, by the closing of the mitral valve, when the right ventricle was 

 similarly injected through the pulmonary artery, the tricuspid valves 

 generally allowed of the escape of the fluid, in streams, more or less 

 copious, in consequence of the incomplete opposition of their margins. 

 On repeating these experiments on different animals the author ob- 

 tained similar results j but found that the imperfection of the valvu- 

 lar function was greater the sooner the heart was examined after the 

 death of the animal j and that if the trials were made after the lapse 

 of a certain time, the rigidity which gradually supervened on the mus- 

 cular fibres of the heart, and of the carneae columnae attached to the 

 margins of the valves, brought them into more complete apposition 

 and led to the accurate closing of the passage. This effect, however, 

 was never so perfectly accomplished in the tricuspid as in the mitral 

 valves. 



The author regards this peculiarity of structure in the tricuspid 

 valve as an express provision against the mischiefs that might result 

 from an excessive afflux of blood to the lungs, operating as a safety- 

 valve against accidents of a serious character, and as more especially 

 advantageous in incipient diseased enlargements of the right ventricle. 

 He adverts to the conditions of the heart during the foetal state of 

 existence, in which the same necessity of guarding against excessive 

 pressure does not occur, and where the structures are found to cor- 

 respond to the variation of functions. A similar adjustment of the 

 right auriculo-ventricular valve to the peculiar circumstances and 

 habits of animals may also be traced by extending the inquiry to va- 

 rious classes of animals. 



