584 



HEART. 



sion of the niusculi papillarcs into two fasciculi ; 

 by their subdivision, on the other hand, into 

 several smaller bundles, but so grouped that 

 the position of the smaller corresponds to the 

 larger; and by the smaller columns furnishing 

 a certain number of the cords usually given off 

 by the larger; yet there appears to be a remark- 

 able similarity between the course and arrange- 

 ment of the chorda; tendinete in all cases. The 

 object of this \ve will afterwards see when 

 inquiring into the precise manner in which 

 these valves prevent regurgitation into the auricle 

 during the systole of the ventricle. The origin 

 of the aorta is furnished with three semilunar 

 valves (Jig. 269), which very exactly resemble 

 in their position, shape, and appearance those 

 placed at the commencement of the pulmonary 

 artery. They are somewhat stronger, and have 

 the corpora sesamoidea generally larger than 

 those in the pulmonary artery. Behind these 

 valves are three dilatations (sinuses i>f Vulsulva) 

 upon the commencement of the aorta, similar 

 to, but more prominent, than those at the com- 

 mencement of the pulmonary artery (Jig. 269). 

 It was maintained by several of the older 

 eminent anatomists that the semilunar valves 

 must necessarily cover the entrance of the 

 coronary arteries,* anil that they were filled, 

 not during the passage of the blood along the 

 aorta, but by the falling back of part of it 

 during the diastole of the heart, or as Boer- 

 haave expressed it, " Hae arterias sunt in dias- 

 tole, dum reliqua? corporis arteriae in systole 

 constituuntur."f Haller mentions two circum- 

 stances which must satisfy every one, if any 

 thing more than the bare inspection of the parts 

 was necessary, that the coronary arteries are at 

 least getitrutly filled in the same manner as the 

 other arteries which arise from the aorta, and 

 these are 1st, the result of experiments on 

 living animals, where the blood is seen to spring 

 per saltum from the cut coronary arteries during 

 the systole of the heart; 2d, when a fa-tus is 

 injected by the umbilical vein, the coronary 

 arteries are also filled. More lately, however, 

 VaustJ has maintained that the origin of the 

 coronary arteries is generally covered by the 

 semilunar valves. lie states that he has injected 

 a great number of hearts from the pulmonary 

 veins; in some of these the injection passed 

 into the coronary arteries, but in by much the 

 greater number these vessels did not contain a 

 single drop of injection. On examination of 

 these cases he found that the semilunar valves 

 entirely covered the origin of the coronary 

 arteries. In attempting to ascertain this point 

 on the uninjected heart, we must bear in mind 

 the different conditions of the aorta in the living 

 body and after death. In the dead body the 

 sinuses ofValsalva are collapsed, so that the 

 semilunar valves can be laid over the origin of 

 the coronary arteries in some cases, where they 



* Morgagni was doubtful in this matter, and 

 thought that he had observed them sometimes 

 covered by the valves, at other times free. Advcrs. 

 v. r Aniuittd>:er. xxv. 



t Institut. Mcd. 183. 



} Rccherches sur la Structure ct les Mouvemcnts 

 du CoMir, p. 22, (1821.) 



would become free when the sinuses are dis- 

 tended as they are with blood in the living 

 body. Making every allowance for this source 

 of fallacy, I am satisfied that I have seen one 

 or two cases in which these valves appeared 

 fairlj to cover the origin of the coronary arteries. 

 Supposing that the origin of the coronary 

 arteries were covered in some instances by the 

 valves, it would in all probability be a matter 

 of little moment, as far as the efficiency of the 

 circulation through these arteries was concerned, 

 as long as the aorta retained its elasticity, for 

 the force with which it drives the distending 

 fluid backwards during the diastole of the 

 heart (a force which can be ascertained in the 

 dead body) would be sufficient to carry on the 

 circulation. The circumstances would, how- 

 ever, become very much altered in those cases 

 which are sufficiently common in advanced 

 age, where the aorta has from .disease of its 

 coats entirely lost its elasticity, and the coronary 

 arteries have also become studded with calca- 

 reous matter, unless we suppose what could 

 scarcely happen, that the blood contained in the 

 sinuses is forced along the arteries when the 

 valves are thrown outwards.* 



Septum af the ventricles. The septum be- 

 tween the ventricles is triangular, and the apex 

 extends to the point of the heart. It is of 

 considerable thickness at the base, but becomes 

 thinner at the apex. Its position is oblique 

 like that of the heart. It is concave towards 

 the right ventricle, and convex towards the left. 

 From the slight rotation of the heart on its 

 axis, the anterior surface of the septum is 

 directed towards the right side, and the posterior 

 towards the left. It is composed, like the other 

 walls of the ventricle, principally of muscular 

 fibres, lined on the one side by the internal 

 serous membrane of the right ventricle, and on 

 the other side by the corresponding membrane 

 of the left. 



We have preferred considering the relative 

 thickness of the parietes, the different capacities 

 of the several cavities of the heart, the relative 

 dimensions of the auriculo-ventricular, aortic, 

 and pulmonary orifices, and the size and weight 

 of the heart under distinct heads, not only as 

 this enables us to obtain a more connected 

 view than we could otherwise have done of 

 points upon which there are many conflicting 

 opinions, and upon which it is so frequently 

 necessary to possess, as far as we possibly can, 

 accurate notions in deciding upon the normal 

 or abnormal state of the organ, but we were 

 also afraid that if mixed up with the other parts 

 of the descriptive anatomy they would have 



* Among the numerous and striking examples 

 which the history of medical science furnishes us 

 of the powerful tendency which preconceived 

 notions have, if not powerfully guarded against, 

 of influencing our observations of the plainest facts, 

 we may instance the statements of Petriolus on this 

 question. He, apparently deeply imbued with the 

 old hypothesis that the heart is the seat of courage, 

 maintained that in bold ;ind carnivorous animals 

 the coronary arteries were above the valves ; in 

 timid and herbivorous animals, on the contrary, 

 they arose behind the valves, while in man they 

 were of uncertain origin, as he was bold or timid. 



