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PLATE XXII.- PACKAGE OF THE VISCERA, AND MESENTERY,
Fig. 1. In this plate the parietes of the chest and abdomen, with the omentum, are removed to show the viscera in situ ; a, the heart; b, the aorta ; c, the descending vena cava ; d, the lungs divided by the mediastinum into two portions; three lobes belong to the right, and two to the left portion of the lungs; e, the diaphragm, or that muscle which separates the thorax from the abdomen; f, the liver ; g, the gall-bladder; h, the stomach; i, the spleen; k, the large intestines ; l, the small intestines ; m, the bladder.
The viscera of the thorax and abdomen, i. e. the viscera of organic life, are irregularly disposed. The agents of volition are double, but the instruments of involuntary motion, namely, the interior life, are single, and at least are irregular in their form.
The several viscera are correctly described in the Theology, and sufficient is said for the purposes for which they are introduced. To the supposed use of the spleen only an objection must be taken: various hypotheses have been entertained as to its office, but none are conclusive; the most probable is, that it is a source of supply of blood for furnishing the gastric secretion, or that the blood undergoes some important change in it.
Fig. 2. The mesentery. This membrane is formed by a reflection of the peritonæum from each side of the vertebræ; it connects the intestines loosely to the spine, to allow them a certain degree of motion, yet retains them in their places; and furnishes their exterior covering. Between the laminæ of, a, the mesentery, are received the glands, vessels, and nerves ; and its extent admits of a projer distribution of each.