192 ANTHROPOLOGY. 



food down the oesophagus, 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 oesophagus itself When the morsels are small, 

 and are mixed with much fluid, the undulating movements from above 

 downwards succeed each other very rapidl}' ; this may be well observed 

 in horses whilst drinking ; large morsels, however, are frequently some time 

 in making their way down. Each portion of food and drink is included in 

 the contractile walls, which are closely applied to it during the whole of its 

 transit. The gurgling sound which is observed when drink is poured down 

 the throat of a person in articulo mortis is due to th^ want of this contrac- 

 tion. The whole of the third stage is completely involuntary. The usual 

 peristaltic movements of the oesophagus are reversed in vomiting ; and this 

 reversion has been observed even after the separation of the stomach from 

 the oesophagus, as a consequence of the injection of tartarized antimony into 

 the veins. At the point where the oesophagus enters the stomach, the 

 cardiac 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 pai'alyzed by the division of the pneumogastric 

 nerve, the food regurgitates into the oesophagus. 



2. 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; it is 

 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 vertebrse, the crura of the diaphragm, and the psoa3 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 peritonaeum 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 ilii, we may 

 define three regions : the epigastric above, the ximbilical in the middle, and 



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