Special anatomy and histology: in two volumes (Volume 2).

  • Horner, William E. (William Edmonds), 1793-1853.
Date:
1846
Catalogue details

Licence: Public Domain Mark

Credit: Special anatomy and histology: in two volumes (Volume 2). Source: Wellcome Collection.

Provider: This material has been provided by the National Library of Medicine (U.S.), through the Medical Heritage Library. The original may be consulted at the National Library of Medicine (U.S.)

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    siderable part of it is, therefore, within the periphery of the lower iibs above, and of the pelvis below. It is completely separated from the cavity of the thorax by the diaphragm, with the exception of the foramina in the latter, for transmitting the aorta, the ascending cava, and the oesophagus. It is bounded, below, by the iliaci interni, the psoas, and the levatores ani muscles; on the front and sides by the five pairs of muscles called abdominal; and behind by the lesser muscle of the diaphragm, the quadrati lumborum, the lumbar verte- brae, and the sacrum. The figure of this cavity is, therefore, too ir- regular to admit of a very rigid comparison with any of the common objects of life; but a little reflection, on the course of its parietes, will make it perfectly understood. It should be borne in mind, that the very great projection of the lumbar vertebra? forms for it a partial vertical septum behind; which, in thin subjects, is almost in contact with the linea alba in front, and may be easily distin- guished through the parietes of the abdomen, when the intestines are empty. The abdominal cavity varies only, inconsiderably, in its vertical diameter, owing to the resistance of the diaphragm above, and of the pelvis below; neither does it change behind, owing to the resis- tance of the spine, the ribs, and the muscles there. But as the in- troduction of food, the development of gaseous substances during digestion, the evolution of the foetus, and many other conditions, re- quire some provision for its undergoing an easy augmentation of volume ; the latter occurs principally forwards and laterally, by the yielding of the muscles and by the extension of their aponeuroses. The diaphragm and the abdominal muscles, for the most part, act alternately ; as the former descends in inspiration the latter relax and give way to the contents of the abdomen ; but in expira- tion, the abdominal muscles contract, and the diaphragm is pushed upwards by the viscera. In attempts at the expulsion of faeces, and in parturition, these muscles contracting, aud the diaphragm being fixed all at the same moment, the cavity of the abdomen is actually much diminished. The viscera contained in the cavity of the abdomen are of three kinds. One kind is engaged in digestion and assimilation ; another in the secretion and excretion of urine ; and the third in generation. As these viscera are numerous, and it is of great importance to determine with precision their position and relative situation, ana- tomists are agreed to divide the cavity of the abdomen into several arbitrary regions. This is the more advantageous, as the bony