Volume 2

The cyclopaedia of anatomy and physiology / Edited by Robert B. Todd.

Date:
1836-59
Catalogue details

Licence: Public Domain Mark

Credit: The cyclopaedia of anatomy and physiology / Edited by Robert B. Todd. Source: Wellcome Collection.

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    organ which could exert no influence on the external form; nor was it to be expected in a muscle which is not wholly voluntary. In this article it is intended to describe, 1st, the form, structure, and organization of the diaphragm ; 2nd, its uses; and, 3rd, its malformations and diseases. Abdominal surface of the diaphragm. Fig. 2. Thoracic surface seen from before. Fig. 3. Thoracic surface sepn from behind, the vertebra being removed. For the convenience of description the dia- phragm is usually divided into two portions— the upper, which is called the costal, or true or greater muscle; and the lower, which is named the vertebral, or smaller, and is also well known as the crura or pillars. This division is sanc- tioned by the situation, the shape, and the uses of the two portions. The upper portion, placed tranversely, (sep- tum transversum,) is thin, but of great super- ficial extent, being connected by its margins to the entire circumference of the inferior outlet of the thorax. Narrow between the sternum and spine, it spreads out on each side into large wings, and its outline bears some resemblance to the figure of eight laid on the side, thus co . The centre is tendinous; the border consists of fleshy fibres. The tendinous part (fig. 1, T) (centrum tendineum, s. nerveum, s. phrenicum, cordiform tendon) is of considerable size, and in shape resembles the trefoil leaf. It presents a large semicircular notch behind towards the spine, and is deeply divided on its anterior margin into three lobes, of which one points for- wards and one to each side. Of these lobes the right is usually the largest, the left the smallest; the anterior is the shortest, and sometimes the broadest; the left is the narrowest and often the longest. But these proportions will be found to vary in different individuals. The tendon is composed of fibres which pursue various courses. The greater number radiate from the vertebral notch; these are crossed by others which run in every direction, and which seem to be continuous with the muscular fibres; and others again appear to be laid on the tendon as accessaries, rather than as con- tributing to its texture. These last are most distinctly seen in old men, and on the under surface of the right lobe. The tendinous centre forms nearly the highest part of the arch. It is less curved than the fleshy portion, and more fixed in its position. One large opening pre- sents itself here, between the right and middle lobes, through which the vena cava passes to the heart. From the anterior and lateral margins of this tendon the muscular fibres pass off in arches, to be inserted into all the base of the thorax by digitations which mix with those of the trans- versus abdominis. Beginning in front, we find two slender fasci- culi running downwards and forwards to the ensiform cartilage. These are separated from each other by a line of cellular tissue, marking the median line of the muscle; sometimes one or both of these bundles may be absent, pro- bably resulting from an arrest of formation. To the outside of these, on each side, a con- siderable triangular interval exists, where the pleura and peritoneum are separated only by cellular substance. Here some small branches of the internal mammary artery pass to the ab- domen ; and in this situation fluids might easily find their way from the cellular tissue of one cavity to that of the other. The fibres next in order, bounding these spaces externally, are much longer; they pass outwards and down- wards to the seventh rib, and are inserted by a