HEART. 



587 



Relative dimensions of the auricula -ven- 

 tricular orifices. The right auriculo-ventricular 

 orifice is larger than the left, as was correctly 

 stated by Portal.* According to Cruveilhier, 

 the largest diameter of the right auriculo- 

 ventricular opening which is antero-posterior 

 is from 16 to 18 lines, and its smallest diameter 

 is 12 lines; while the largest diameter of the 

 left auriculo-ventricular opening, which is di- 

 rected almost transversely, is from 13 to 14, 

 and its smallest is from 9 to 10 lines. Bouillaud 

 gives the results which he obtained from the 

 accurate measurement of the circumference of 

 these two openings in three perfectly healthy 

 hearts. The average circumference of the left 

 auriculo - ventricular opening was 3 inches 

 6^ lines : the maximum was 3 inches 10 lines, 

 and the minimum was 3 inches 3 lines. The 

 average circumference of the right auriculo- 

 ventricular opening was 3 inches 10 lines : the 

 maximum was 4 inches, and the minimum 

 was 3 inches 9 lines. 



Circumference of the aortic and pulmonary 

 orifices. The circumference of the aortic and 

 ventriculo - pulmonary orifices is sometimes 

 nearly equal ; more generally, however, the 

 ventriculo-pulmonary is the larger. Bouillaud 

 gives the following measurements of these 

 openings taken from four healthy hearts : 

 Average circumference of the aortic opening, 

 2 inches 5$ lines: the maximum 2 inches 

 8 lines, and the minimum 2 inches 4 lines. 

 Average circumference of the ventriculo-pul- 

 monary opening, 2 inches 7f lines : the 

 maximum 2 inches 10 lines, and the minimum 

 2 inches 6 lines. I have found this difference 

 between the circumference of these two open- 

 ings marked distinctly at seven years of age. 

 M. Bizot has given measurements of the ar- 

 terial orifices, of which the following is the 

 average. 



Aortic orifice, male. 



Average from 16 to 79 years. . 45$ lines. 



Aortic orifice, female. 



Average from 16 to 89 years . . 41 lines. 

 Pulmonary orifice, male. 



Average from 16 to 79 years . . 54^ lines. 

 Pulmonary orifice, female. 



Average from 16 to 89 years . . 48 j lines. 



Size and weight. Laennec has stated that 

 the size of the heart in general nearly corre- 

 sponds to the closed fist of the individual. 

 This can only be considered as a loose ap- 

 proximation, as the size of the hand may vary 

 in different individuals otherways resembling 

 each other, either from original conformation 

 or from dissimilar modes of life ; and, besides, 

 the size and form of the healthy heart itself 

 may vary sufficiently to effect an apparent 

 difference in these respects. 



The average length of the heart, according 

 to Meckel, is 5 inches, of which about 

 4 inches are to be allowed for the ventricles, 

 and 1 2 inch for the auricles. Bouillaud found 

 that a line drawn from the origin of the aorta 

 to the point of the heart ranged, in nine 



* Anatomic Medicalc, t. iii. p. 69. 



healthy hearts, from 4 inches to 3 inches 

 2 lines. The average length was 3 inches 

 7^ lines. 



The weight of the heart, according to 

 Meckel, is about 10 ounces, and its propor- 

 tionate weight to the whole body is as 1 to 200. 

 Tiedemann is of opinion that the proportionate 

 weight of the heart to the body is as 1 to 

 160.* The weight of the healthy and empty 

 heart, according to Cruveilhier, is from 7 to 

 8 ounces. Bouillaud found the average weight 

 in thirteen healthy hearts to be 8 ounces 

 3 drachms. According to Lobstein it weighs 

 between 9 and 10 ounces. The size and 

 weight of the heart must generally be to a 

 great extent in conformity with the size and 

 weight of the body. In an athletic male we 

 would expect it to weigh about 10 ounces, in 

 an ordinary-sized individual about 8 ounces, 

 and in weakly persons, or in cases of pro- 

 tracted debility, it would be still more dimi- 

 nished in weight. For the same reason it is 

 generally larger and heavier in males than 

 in females. 



Structure of the heart. The heart consists 

 of muscular and tendinous textures, of cellular 

 tissue, of bloodvessels, of nerves, and of lym- 

 phatics, enclosed between two serous mem- 

 branes. 



Tendinous texture. The tendinous texture 

 of the heart is placed, 1, around the auriculo- 

 ventricular and arterial orifices ; 2, within the 

 reduplicature of the lining membrane forming 

 the auriculo-ventricular and arterial valves; 3, 

 it forms the chordae tendineae. 



Auriculo-ventricular tendinous rings. 

 Around each auriculo-ventricular opening we 

 find a tendinous circle or ring, from the upper 

 part of which the muscular fibres of the au- 

 ricles arise, and from the lower part those of 

 the ventricles, thus affording perhaps the only 

 example in the human body of a strictly in- 

 voluntary muscle having tendinous attach- 

 ments. The tendinous ring surrounding the left 

 auriculo-ventricular opening is stronger than 

 that surrounding the right. These tendinous 

 zones are thicker along the lower edge where 

 the muscular fibres of the ventricle are attached, 

 and become thinner along the upper edge where 

 the muscular fibres of the auricles are attached, 

 so that the fat occupying the auricular groove 

 is seen through the upper portion of the ring 

 on the right side. The right margin of the left 

 auriculo-ventricular ring is connected with that 

 surrounding the aortic opening. The existence 

 of the auriculo-ventricular and arterial tendi- 

 nous rings was well known to Lower.f 



Arterial tendinous rings. The form of the 

 tendinous rings surrounding the arterial open* 

 ings, and the manner in which the large arte- 

 ries are attached to their upper edges, have not, 

 I think, been described with sufficient accu- 

 racy. These textures are very plainly observed 



* If we consider the ordinary weight of an adult 

 heart to be 8 ounces, and the average weight of 

 the whole body to be 150 Ibs. the proportionate 

 weight of the heart to the body would be as 1 

 to 225. 



t Tractatus De Corde, p. 29. 1669. 



