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CHAPTER XI. 
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 kings divi¬ 
ded 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 smallintestines; w, the bladder. 
The viscera of the thorax and abdomen, i. e. the viscera of or¬ 
ganic life , are irregularly disposed. The agents of volition are 
double, but the instruments of involuntary motion , namely, the in 
terior 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 un¬ 
dergoes some important change in it. 
Fig. 2. The mesentery. This membrane is formed by a reflec¬ 
tion of the peritonceum from each side of the vertebra; it connecrs 
the intestines loosely to the spine, to allow them a certain degree 
of motion, yet retains them in their places; and furnishes their ex¬ 
terior covering. Between the laminae ofj a, the mesentery, are re¬ 
ceived the glands , vessels , and nerves; and its extent admits of a 
proper distribution of each. 
