192 ANTHROPOLOGY. 
food down the cesophagus, then commences. This is accomplished in the 
upper part, by means of the constrictors of the pharynx; and in the lower, 
by the muscular coat of the cesophagus itself. When the morsels are small, 
and are mixed with much fluid, the undulating movements from above 
downwards succeed each other very rapidly ; this may be well observed 
in horses whilst drinking; large morsels, however, are frequently some time 
in making their way down. Hach portion of food and drink is included in 
the contractile walls, which are closely applied to it during the whole of its 
transit. The Sadie sound which is observed when drink is poured down 
the throat of a person in articulo mortis is due to the want of this contrac: 
tion. The whole of the third stage is completely involuntary. The usual 
peristaltic movements of the cesophagus are reversed in vomiting; and this 
reversion has been observed even after the separation of the stomach from 
the cesophagus, as a consequence of the injection of tartarized antimony into 
the ves. At the point where the cesophagus enters the stomach, the 
eardiac orifice of the latter, there is a sort of sphincter, which is usually 
closed. This opens when there is a sufficient pressure on it, made by accu- 
mulated food; and afterwards closes, so as to retain the food in the stomach. 
The opening of the cardia is one of the first acts which take place in vomit- 
ing. When the sphincter is paralyzed by the division of the aes + 
nerve, the food regurgitates into the cesophagus. 
9. ORGANS OF ASSIMILATION. 
The organs concerned in digesting the food, after it has been masticated 
and swallowed, are the stomach and intestines, assisted by various glands. 
We shall precede the detailed description of the viscera of the abdomen, 
‘by a brief reference to its regions, as established by authors. The abdomen 
is the largest cavity in the body; it is of an oval form; its capacity, and in 
‘some degree its figure, differ at different ages, and in different subjects; itis 
bounded superiorly by the diaphragm, anteriorly and laterally by the ab- 
‘dominal muscles, inferiorly by the true and false pelvis, and posteriorly by 
the lumbar vertebre, the crura of the diaphragm, and the psoz and the qua- 
drati lumborum muscles. Although the expression ‘‘cavity of the abdomen” 
is in common use, it is not correct; for during life there is no cavity, as the 
diaphragm and abdominal muscles, by their alternate action, keep up such a 
constant and uniform pressure on the viscera, that these and the parietes 
are always in perfect contact. The abdomen contains the peritoneum and 
the organs of digestion; the kidneys, renal capsules, and ureters; also the 
lacteals or absorbent vessels, with their glands, and the thoracic duct, the 
‘sympathetic nerves, the aorta, vena cava, and the numerous branches of 
these vessels. The abdomen is generally divided by writers into nine, but 
by some into twelve regions; by drawing two transverse lines, one between 
the extremities of the cartilages of the ninth or tenth ribs, and the other 
between the anterior superior spinous processes of the ossa ili, we may 
define three regions: the epigastric above, the umbilical in the middle, and 
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