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ABNORMAL CONDITIONS OF THE HEART. 



trophy, and may result from the violence of 

 contraction of the enlarged ventricle. Dilata- 

 tion of the aorta at its commencement and its 

 arch is frequently the consequence of this dis- 

 ease in the left ventricle, and dilatation of the 

 pulmonary artery ensues upon it in the right 

 ventricle. 



Dilatation of the cavities of the heart. 

 " V\ hen the heart is incapable of sufficiently 

 expelling its contents, whether in consequence 

 of obstruction in the vessels from it, of regurgi- 

 tation into it through imperfect valves, of want 

 of power, of irritability, or of both, it becomes 

 distended, and in time permanently dilated."* 

 We have already described that kind of dilata- 

 tion which is the most common, namely, that 

 accompanied by hypertrophy ; dilatation also 

 occurs in connexion with an opposite condition 

 of the parietes, namely, attenuation of them. 

 The muscular tissue has lost its tone, and 

 yields, as it were, without resistance to the dis- 

 tending force. It is laid down by authors that a 

 third variety of dilatation may exist, what they 



spot so often seen upon the external surface of 

 the right ventricle is an almost invariable at- 

 tendant upon the dilated heart. Dilatation, 

 may affect any or all of the heart's cavities ; but 

 it is met with by far the most frequently in the 

 right ventricle, and very commonly both ven- 

 tricles are dilated, in which case the right cavity 

 is generally more capacious than the left. 



An extreme case of dilatation is afforded in 

 an example quoted by Bouillaud : " the right 

 cavities were so dilated and their walls so at- 

 tenuated, that the auricle was converted into a 

 kind of transparent membrane, and the ventricle 

 was reduced only to the ordinary thickness of 

 the auricle." 



In determining as to the degree of attenua- 

 tion of the walls which may accompany any 

 particular case of dilatation of the auricles, the 

 anatomist must bear in mind that even in the 

 natural state the interval between the musculi 

 pectinati of the right auricle is only composed 

 of the endocardium and pericardium, separated 

 by a very fine and transparent cellular tissue, 



call simple dilatation, or that in which, while and by a few muscular fibres crossing obliquely 

 the cavity is dilated, the parietes are of their na- from one pectinate muscle to the next one. I 



tural si2e. It seems to me impossible that any 

 cavity of the heart can, in a dilated state, conti- 

 nue of the natural thickness without hypertrophy, 

 in the absence of which dilatation implies neces- 

 sarily a diminution in thickness; during dia- 

 stole the parietes of the heart's cavities are thin- 

 ner than during systole ; what a contracted 

 muscle gains in one dimension it loses in ano- 

 ther ; and the same may be said of a relaxed or 

 distended muscle. Again, if we contrast a con- 

 tracted with a dilated bladder, it seems evident 

 that we cannot innate the former, however in- 

 completely, without producing a manifest dimi- 

 nution in the thickness of its walls. Hence I 

 infer, that if the parietes of any cavity be per- 

 fectly natural, they must become thinned under 

 the influence of the force which produces the 

 dilatation; and, on the other hand, if we find 

 that the parietes of a dilated cavity possess the 

 normal thickness, we may be assured that it is 

 slightly hypertrophous. It appears then to be 

 most correct to limit the varieties of dilatation 

 to two, that with hypertrophy and that with 

 attenuation, or the passive aneurism of Corvisart. 

 In this latter form of dilatation, then, we see 

 a manifest alteration of the muscular tissue; it 

 is paler, softer, less resisting, less elastic than 

 natural. When the heart is emptied of its con- 

 tents, the walls do not at all return upon them- 

 selves, but remain flaccid ; nor when cut do 

 they show any disposition to retract ; and it is 

 this state of the muscular substance which will 

 serve best to enable the anatomist to distinguish 

 morbid dilatations from those which result from 

 mechanical distension of the cavity by a coagu- 

 lum formed at the time of death. An obvi- 

 ously diseased state of both the internal and 

 external membranous coverings of the heart is 

 constantly present along with this form of dila- 

 tation. These membranes lose their transpa- 

 rency in several parts, apparently from some 

 abnormal deposit subjacent to them : the white 



Dr. Williams, loc. cit. 



have twice seen a perfectly natural right auricle 

 carefully put up as a museum specimen of 

 morbid attenuation of the parietes, owing to 

 ignorance or forgetfulness of this fact. 



Dilatation of' the orifices of the heart. As a 

 natural result of dilated cavities we meet with 

 dilated orifices of the heart, and the enlarge- 

 ment of which again produces in many cases 

 insufficiency of the valves. Bouillaud gives 

 the measurement of the auriculo-ventricular 

 orifice (which is the most liable to dilatation) 

 in three hearts ; in one it measured five inches 

 in circumference, and in another four inches 

 three lines, while in a third the dilatation was 

 stated to be so great that the tricuspid valve 

 could not be closed. 



Aneurism of the heart. A diseased state of 

 the heart occurs not unfrequently, strongly 

 analogous to that which under the same name 

 is so well known as occurring in the arterial 

 system. Most of the varieties too of arterial 

 aneurism find their analogues in the heart: 

 thus we have, 1. the aneurism by simple dila- 

 tation, or true aneurism, resulting from partial 

 dilatation of one of the heart's cavities; 2. 

 the false aneurism or that resulting from rup- 

 ture of one or more of the textures entering 

 into the formation of the heart's parietes ; 3. 

 we find the dissecting aneurism analogous to 

 that remarkable form of arterial aneurism 

 first described by the late Mr. Shakelton ; 4. 

 not improbably, we also meet with what is 

 analogous to the varicose aneurism, and may 

 be designated spontaneous varicose aneurism of 

 the heart. To the zeal and acuteness of Mr. 

 Thurnam * morbid anatomists are much in- 

 debted for his having arranged, compared, and 

 classified a considerable number of cases of 

 aneurismal dilatations connected with the heart, 

 either observed by himself, or preserved and 



* Vide his valuable monograph on Aneurisms of 

 the Heart in Med. Chir. Trans, vol. xxi. An ap- 

 pcndix containing references to cases is added. 



