The diseases of the heart and of the aorta / by Thomas Hayden.

  • Hayden, Thomas.
Date:
1875
Catalogue details

Licence: Public Domain Mark

Credit: The diseases of the heart and of the aorta / by Thomas Hayden. Source: Wellcome Collection.

    24/1254 (page 6)
    fibrinous exudation upon the epithelial surface, which here, as upon other portions of the surface of the heart, has invariably, in my experience, presented the polished and glistening appear- ances characteristic of its healthy condition. They arise, mani- festly, from chronic irritation of the superficial surface of the heart, the result of excessive and long continued friction, to whatever cause due. Persons long engaged in some bodily labour, involving great muscular strain and habitual distention of the right chambers of the heart, are most likely to exhibit typical milk spots. Hence, their usual position on the ante- rior surface of the right side of the heart, opposite the unyield- ing surface presented by the sternum. Examined microscopically, the subserous lamina of the peri- cardium is found to consist mainly of white fibrous tissue, the fasciculi of which overlie and interlace with one another at all conceivable angles. It includes, also, a large proportion of yel- low elastic tissue, composed of fine curling filaments of an aver- age diameter of l-17,000th part of an inch. This latter tissue confers upon the pericardium in an eminent degree the property of elasticity, in virtue of which it is capable of accommodating itself to variations in volume of the several chambers of the heart, during contraction and relaxation respectively. The capa- city of the pericardium is accurately adapted to the volume of the heart at all periods of cardiac action. Its walls are there- fore constantly in a state of tension during the continuance of cardiac movement, no less during the systole than the diastole of the ventricles. This accuracy of adaptation of the pericardium is, no doubt, mainly clue to the constancy of volume of the heart at all periods of its action, a circumstance to be attributed to the alternating contraction and relative capacity of the auricles and ventricles, and of the roots of the great vessels connected with them, and included within the pericardium. If the chest of a still living animal be laid open, it will be found impossible to pinch up the pericardium between the finger and thumb, and difficult even by means of a pair of good forceps, as long as the heart continues to pulsate. The purposes of the pericardium seem to be to insulate the