A system of human anatomy : on the basis of the "Traité d'anatomie descriptive" of H. Cloquet / by Robert Knox.

  • Cloquet, H. (Hippolyte), 1787-1840.
Date:
1831
Catalogue details

Licence: Public Domain Mark

Credit: A system of human anatomy : on the basis of the "Traité d'anatomie descriptive" of H. Cloquet / by Robert Knox. Source: Wellcome Collection.

Provider: This material has been provided by the Francis A. Countway Library of Medicine, through the Medical Heritage Library. The original may be consulted at the Francis A. Countway Library of Medicine, Harvard Medical School.

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    descend from these parts to the thorax. The sterno-hyoidei and sterno-thyroidei muscles are inserted mto it. 105. The lower circumference or base of the thorax, is very large, especially in the transverse direction. It presents, anterior- ly a considerable notch, in the middle of which is the xiphoid car- tilage, and which is formed laterally by the union of the cartilages of the false ribs, which constitute a sort of convex border, inter- rupted between the tenth, eleventh, and twelfth ribs on each side. Posteriorly, the base of the chest has also two small notches, which are owing to the inclination of the last rib upon the vertebral column. In other respects it does not descend so low anteriorly as on the sides and posteriorly. It gives insertion to several of the abdominal muscles, especially to the transversales muscles and the diaphragm. 106. Direction of the Thorax. The axis of the cone represented by the thorax, or the ideal line which falls perpendicularly upon the middle of its base, is oblique from above downwards, and from behind forwards. But all the walls of the chest do not equally concur to produce the obliquity, which especially depends upon the circumstance that the anterior wall retires from the spine in proportion as it descends. There results from this, that a line as- cending vertically from the centre of the base of this cavity, would not pass through the middle of its summit, but would pierce the upper part of the sternum. 107. Dimensions of the Thorax. In tile skeleton, the height of this cavity appears much greater than in the body invested with its soft parts, because, in the latter state, the diaphragm ascends pretty high in its interior. It is measured by means of certain ideal lines, named its diameters, which pass from the sternum to. the vertebral column, or from one side to the other. All the dia- meters are greater below than above. It is also observed, that the concavity of the v^tebral column augments the dimensions of the antero-posterior diameters in the middle. This is far, however, from compensating the loss which they experience from the pro- jection of the bodies of the vertebrae ; so that these diameters are much greater laterally than in the median line. The dimensions of the chest vary extremely in different indivi- duals. They also experience great variations according to age or sex. The height of this part of the trunk is smaller, but its breadth is greater, in woman than in man. 108. Although, as we have already said, the thoracic cavity is generally symmetrical, in other words perfectly similar on both sides, it yet sometimes happens that one of its sides is more capa- cious and stronger than the other, and even that it forms a re- markable projection, without this phenomenon being attributable to any original malformation, or to disease.