Licence: Public Domain Mark
Credit: Croonian lecture / by James Pettigrew. Source: Wellcome Collection.
Provider: This material has been provided by The University of Glasgow Library. The original may be consulted at The University of Glasgow Library.
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![Commencing with the left ventricle, which he believes to be the typical one, the Lecturer stated that, by exercising a little care, he had been enabled to unwind as it were its muscular substance, and so to separate its walls into several layers*, each of which is charac- terized by a difference in direction. Seven layers, at least, can be readily shown by dissection; but he believes they are in reality nine; viz. four external, the fifth or central, and four internal. He explained how the external fibres are continuous with the internal fibres at the apex, as was known to Lowerf, Gerdyif, and others, and how the fibres constituting the several external layers are con- tinuous with corresponding internal layers likewise at the base§,— a i'act to which the Lecturer drew particular attention, as being con- trary to the generally received opinion, which is to the effect that the fibres at the base are non-continuous, and arise from the auriculo- ventricular tendinous rings—which, as he showed by numerous dis- sections, is not the case. Coming next to the question of the direction of the fibres, he showed how there is a gradational sequence in the direction of the fibres constituting the several layers. Thus the fibres of the first layer are more vertical in direction than those of the second, the second than those of the third, the third than those of the fourth, and the fourth than those of the fifth, the fibres constituting which layer are transverse, and run at nearly right angles to those of the first layer. Passing the fifth layer, which occupies the centre of the ventricular wall and forms the boundary between the external and internal layers, the order of things is reversed; and the remain- ing layers, viz. six, seven, eight, and nine, gradually return to the vertical in an opposite direction, and in an inverse order. This re- * Senac (Traite de la Structure du Coeur, &.c. [Paris, 1749], planche 8) figures four layers; and Searle (Cyc. of Anat. and Phys., art. Heart) speaks of three, t Tractatns de Corde, &c. London, 1609. X Reclierches, Discussions et Propositions d'Anatomie, Physiologic, &c. Paris, 1823. § The late Dr. Duncan, Jun., of Edinburgh, was aware of the fibres forming loops at the base, but seems to have had no knowledge of the continuity being occasioned by the union of corresponding e.vtei-nal and internal layers, or that these basal loops were prolongations of like loops formed by similar correspond- ing external and internal layers at the apex—a point which the Lecturer believes he is the first to establish.](https://iiif.wellcomecollection.org/image/b21476470_0004.jp2/full/800%2C/0/default.jpg)
