HEART. 



589 



from the posterior or left, and a, great part of the 

 anterior, in fact to that part of the tendinous 

 ring which separates the aortic from the auri- 

 culo-ventricular opening. From the posterior 

 part of that portion of the tendinous ring to 

 which the mitral valve is connected, the ante- 

 rior fibres of both auricles, near the septum, 

 arise. As the left tendinous ring is thicker and 

 narrower than the right, there is a larger space 

 left between the fixed edge of the valves and 

 the attachment of the middle coat of the arte- 

 ries than there is on the left side. This space 

 is of some importance, as upon it a consider- 

 able part of the pressure of the column of 

 blood in the large arteries must be thrown 

 during the diastole of the ventricles. 



There is a good representation of these ten- 

 dinous rings given in Tab. II. Opera Valsalvae, 

 torn. i. At page 129 they are thus described : 

 " In horum sinuum ambitu qua valvulae si- 

 nubus annectuntur quidem quasi Agger videtur 

 occurrere substantial durioris ad similitudinem 

 cartilaginis tarsi palpebraruin." I find also 

 that Gerdy* appears to have had an accurate 

 notion of the form and appearance of these ten- 

 dinous rings. He was aware of the existence 

 of the projecting angles of the tendinous ring 

 which pass up between the festoons of the 

 middle coat of the arteries, and which have 

 been overlooked in succeeding descriptions. I 

 find also that the late Dr. A. Duncan, jun. has, 

 in his unpublished manuscript, given a very 

 accurate account of these structures in the heart 

 of the ox. 



Tendinous structure in the auriculo-ventri- 

 cular valves. Distinct tendinous fibres exist 

 in the auriculo-ventricular valves enclosed be- 

 tween the reduplication of the lining serous 

 membrane. These are continuous with the 

 auriculo-ventricular tendinous zones, and are 

 most distinct and of great strength at the base. 

 I could never observe any distinct traces of mus- 

 cular fibres in these valves in the human heart 

 either when fresh or after long boiling. Bouil- 

 laud has, from the examination of one incon- 

 clusive case, but principally from analogy with 

 the corresponding valves of the heart of the ox, 

 supposed that they may exist in some cases in 

 hypertrophy of the valves. In making exami- 

 nations of this kind we must be exceedingly 

 careful not to mistake the tendinous fibres 

 when tinged with blood for muscular fibres, 

 for under these circumstances they certainly at 

 all times assume the appearance of muscular 

 fibres .f 



* Journal Complementaire, torn. x. 



t In the heart of the dog 1 have seen a distinct 

 band of transverse muscular fibres in the base of 

 the larger lip of the mitral valve, but could never 

 satisfy myself of the existence of any longitudinal 

 muscular fibres. In the heart of the ox and horse 

 very distinct longitudinal muscular fibres are seen 

 in the valves of both sides of the heart, princi- 

 pally, if not entirely, continuous with the inner 

 layer of the fibres of the auricles. A greater part 

 pass over the inner surface of the tendinous rings, 

 and are firmly attached to the tendinous structure 

 of the valves, reaching nearly to the lower margin 

 of the smaller segments of the valves. The effect 

 of these fibres upon the movements of the valves 

 would form an interesting subject of investigation. 



Tendinous structure in the arterial valves. 

 Distinct tendinous fibres also exist in the arte- 

 rial valves, which must add considerably to 

 their strength and prevent their more frequent 

 rupture. Three of these tendinous bands in 

 each valve are stronger than the others, and 

 their position deserves attention, as they are 

 often the seat of disease. One of these 

 bands occupies the free margin of the valve, 

 and passes between the projecting extremities 

 of the tendinous festoons (Jig. 270, a). Upon 

 the middle of this band the corpus .Arantii, 

 which is formed of a similar texture, is placed. 

 The other band cornes from a point a little 

 above the middle of the projecting end of the 

 tendinous festoon (fg. 270, b), and passes 

 up in a curved manner towards the corpus 

 Arantii, leaving between it and the superior 

 band a triangular space on each side, in which, 

 if any tendinous fibres exist, they are exceed- 

 ingly obscure. These two tendinous bands 

 were well known to Morgagni. The third 

 band is placed in the attached margin of the 

 valve, and renders this part the thickest and 

 strongest. Between the middle band and the 

 attached margin of the valve a number of 

 weaker bands are placed, which also pass up- 

 wards, generally assuming a curved form. Mor- 

 gagni termed these lower and weaker fibres^/v? 

 carne&j but they evidently belong to the same 

 structure as the stronger bands. The arrange- 

 ment of these tendinous fibres is best seen in 

 the aortic valves, and the appearance exhibited 

 in the accompanying representation, (jig. 270,J 



Fig. 270. 



which has been taken from Morgagni, is not 

 always distinctly observed, where the valves 

 are perfectly healthy, but become sufficiently 

 obvious in certain cases of disease. 



Attachment of' the middle coat of the arte- 

 ries to the arterial tendinous rings. The inner 

 and outer serous membranes are continued from 

 the heart upon the arteries ; the one becoming 

 the inner coat of the arteries, and the other is 

 continued for a short distance upon their ex- 

 ternal surface. A thin layer of cellular tissue 

 also passes from the heart along the arteries 

 between their middle coat and their external 

 serous membrane. These are, however, so far 

 unimportant compared with the attachment of the 

 middle coat of the arteries to the tendinous fes- 

 toons which we have just described. The middle 

 coat is so very firmly and strongly attached both 

 to the external edges and to the anterior portion 

 of the upper part of these projecting extremi- 

 ties, (fig. 267, d,) that it can be detached with 

 great difficulty. Those fibres of the middle 

 coat attached to the projecting extremities, 



