VESSELS AND NERVES SIZE AND WEIGHT. 321 



remarkable in the adult, does not exist at an early period in the foetus. An examina- 

 tion of the foetal heart, therefore, shows a much greater similarity in the mode of 

 arrangement of the layers of fibres in the walls of the two ventricles than might be 

 supposed from the examination of the adult. 



It is to be observed, in conclusion, that Pettigrew's observations were made almost 

 exclusively upon the hearts of animals. No doubt many circumstances are nearly 

 similar in the human heart, but it is still desirable that a fuller examination of the 

 structure of the human heart should be made, and more especially that this subject 

 should be investigated in connection with its development. 



(C. F. Wolff, De ordine fibrarum Muscularium Cordis ; Act. Acad. Petropol. 1780 

 1792. Gerdy, Rech. &c. d' Anatomic, Paris, 1823. J. Reid, Art. "Heart/' in 

 Cyclop, of Anat. and Physiol. Searle, Art. " Fibres of the Heart," in the same. 

 J. Pettigrew, in Philos. Trans. 1864.) 



VESSELS AND NERVES. 



The blood-vessels and nerves of the heart will only be shortly noticed in this place, 

 as a fuller description of them will be given along with those parts of the vascular 

 and nervous systems from which they respectively take their origin. 



Vessels. The substance of the heart receives its blood through the two coronary 

 arteries, which arise respectively from the two anterior aortic sinuses of Valsalva. 

 The coronary veins terminate in the right auricle. Besides the great cardiac or 

 coronary vein, and another principal branch, there are two smaller orders of veins 

 opening separately into the right auricle. The stems and larger divisions of these 

 vessels run principally in the great transverse and longitudinal grooves of the heart ; 

 from these grooves and other parts of the external surface the smaller branches 

 penetrate into every part of the muscular substance. 



Nerves. The nerves given off by the cardiac plexuses, appear rather small in com- 

 parison with the bulk of the heart ; they are derived partly from the cerebro-spinal 

 and partly from the sympathetic system, more especially from the pneumogastric nerve, 

 ancl from the cervical and superior dorsal ganglia of the sympathetic nerve. Besides 

 the larger ganglia in the cardiac plexuses at the base of the heart, the nerves present 

 minute ganglia at different points along their course in its substance, which have been 

 figured and described by Remak. The nerves course obliquely downwards on the 

 ventricles of the heart, decussating with the superficial fibres, between which and the 

 pericardium are situated their main branches and the ganglia of Remak. (Remak ; 

 Froriep's Notizen, 1838, p. 137; and Muller's Archiv. 1844, p. 463, taf. xii.) 



WEIGHT AND DIMENSIONS OF THE HEART. 



The size and weight of the heart, the thickness of its walls, the capacity of its 

 several cavities, and the width of its great orifices, have been made the subject of 

 extensive observation, more especially with the view to determine some standard 

 dimensions with which to compare the deviations occurring in disease. 



Size. It was stated by Laennec, as the result of his experience, that the heart in 

 its natural condition was about equal in size to the closed hand of the individual. 

 It is about five inches long, three and a half in its greatest width, and two and a 

 half in its extreme thickness from the anterior to the posterior surface ; but linear 

 measurements of a flaccid organ like the heart must be subject to so many accidental 

 variations as to render them of little value. 



Weight. The average weight of the heart in the adult is also subject to consider- 

 able variation, ranging between rather wide limits, which depend on the general 

 weight of the body and on the sex. 



Its mean weight has been variously stated by different authors, as from 7 oz. up 

 to 10 oz. ; but, according to tables published by Reid, the average weight in the 

 adult male is as high as 11 oz., and in the female as 9 oz. ; while according to Peacock 

 the average of the male is 9| oz., and that of the female 9 oz. 



The weight of the heart maintains some general proportion to that of the body. 

 According to Tiedemann this is about 1 to 160; by Clendinning it was found to be 

 1 to 158 in males, and 1 to 149 in females ; and by Reid to be 1 to 169 in a series of 

 thirty-seven males, and 1 to 176 in twelve females ; but in the healthy males dying 

 suddenly the ratio was as 1 to 173. 



