792 DR PETTIGREW ON THE RELATIONS, STRUCTURE, AND FUNCTION, 



other. The vital theory which was espoused by Mayo and Bouillaud,* has been 

 defended with great abiUty by Dr John REiD,f who says, that if the lips of the 

 valves were merely floated up to the orifice, a greater quantity of the blood 

 would regurgitate into the auricles during the systole of the ventricle than if 

 the lips were assisted or brought together by an active force. This author 

 alludes to, and very properly attaches considerable importance to the fact, that 

 the musculi papillares to which the valves are attached by the chordse tendinese, 

 contract with the other portions of the ventricular walls. He also points out the 

 uniform position and course of the musculi papillares and chordae tendinese, and 

 shows, as bearing directly upon the question, how the chordse tendineae in the 

 left ventricle pass from each musculus papillaris to both lips of the mitral valve. 

 One statement, however, made by him requires to be noticed. When speaking 

 of the mitral valve he says, that the lip of the posterior or smaller segment 

 though it maybe drawn inwards so as to meet that of the larger and more move- 

 able one, is so bound down as to he scarcely capable, in most cases, of being floated 

 up on a level ivith the oriflce. I have examined a large number of hearts, young 

 and old, human and otherwise, with a view to determine this point, and in no 

 instance do I remember an example where the peculiarity adverted to was 

 observable. The anterior or larger segment, from its attachments and shape, 

 naturally rises higher, just as the anterior and septal segments of the tricuspid 

 valve for similar reasons, rise higher than the posterior segment ; but in every 

 case, the posterior or smaller segment rises sufficiently high, not only fairly to 

 meet the anterior and larger one, but if a sufficiency of pressure is exercised, 

 to protrude in an upward direction, so as to form a convexity which encroaches 

 upon the left auricular space. 



In the valvular controversy, as in most others, a certain amount of truth is 

 to be found on either side; and I have to express my conviction, that both 

 theories (conflicting though they appear) are virtually correct as far as they go, 

 but that neither the one nor the other is sufficient of itself to explain the gradual, 

 and to a certain extent self-regulating process, by which the auriculo-ventricular 

 valves are closed and kept closed. On the contrary, I believe that the closure is 

 effected partly by mechanical and partly by vital means. In other words, that 

 the blood towards the end of the diastole and the beginning of the systole forces 

 the segments in an upward direction, and causes their margins and apices to be 

 so accurately applied to each other as to prevent even the slightest regurgita- 

 tion; whereas, during the systole, and towards the termination of that act, 

 the valves are by the contraction of the musculi papillares, dragged down by 



* These investigators proposed to call the musculi papillares the tensor, elevator, or adductor 

 muscles of the valves. 

 f Op. cit. pp. 361, 362. 



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