380 THE DIGESTIVE APPARATUS IN MAMMALIA. 



evident towards the insertion of the oesophagus into the stomach, and that 

 the muscular tube is at this point so narrow, that it is almost exactly filled 

 by the folds of mucous membrane it contains. For this reason it is that 

 we may inflate a stomach by the pylorus, without applying a ligature to 

 the cesophagus ; the aperture of the canal being so perfectly closed that it 

 does not allow a bubble of air to escape. In describing the interior of the 

 stomach, we wiU refer to the consequences resulting from this interesting 

 anatomical fact. 



Vessels and nerves. — The cesophagus is supplied with blood by the 

 divisions given off by the common carotid artery, as well as the bronchial 

 and oesophageal arteries. The nerves are almost exclusively derived 

 from the pneumogastric ; the motor nerves are the superior oesophageal 

 filaments, branches of the external pharyngeal and laryngeal ; the sensitive 

 filaments are derived from the recurrent. 



Functions. — This canal conveys nutriment from the pharynx to the 

 stomach ; it has no other uses. , 



DIFFERENTIAL CHAEACTEKS OF THE (ESOPHAGUS IN OTHEK THAN SOLIPED ANIMALS. 



In all the other domesticated animals, the muscular coat is red-coloured throughout 

 its whole extent, and everywhere offers the same degree of thickness and the same 

 flaccidity, The canal is also as wide towards the stomach as at tlie pharynx. In 

 Ruminants and tlie Caruivora, it enters the stomach as a funnel-shaped (infundi- 

 buliform) tube. 



The dilatability of the oesophagus is very remarkable in these animals : Dogs swallow 

 large pieces of flesh; and Cows and Oxen are-able to injest large turnips, or suoli 

 voluminous foreign bodies as shoes. 



(In Ruminants and the Garnivora the oesophagus is, proportionally, wider than in the 

 Horse and Pig.) 



COMPABISON OP THE CESOPHAGUS OF MAN WITH THAT OF ANIMALS. 



The oesophagus of Man resembles that of Carnivora ; its diameter is almost uniform. 

 It also inclines to the left below the neck, but in the thorax is in the median line, though 

 it again deviates to the left as it joins the stomach. As the thyroid in Man is very 

 voluminous, it is related to the cesophagus in the upper part of the neck. Two small 

 accessory fasciculi, belonging to the muscular tunic of the cesophagus, have been 

 described : one is the hroncho-cesophageal muscle, which is detached from the left bronchus ; 

 and the other the pleuro-aesophageal muscle, detached from the left layer of the posterior 

 mediastinum. 



Article II. — The Essential Organs of Digestion. 



These organs being all contained in the abdominal cavity, this common 

 receptacle will first be studied ; afterwards the stomach, intestines, and their 

 annexed organs — the liver, pancreas, and spleen — will be described. 



THE ABDOMINAL CAVITY. 



In mammalia, the interior of the trunk is partitioned by the diaphragm 

 into two great cavities, that lodge the majority of the organs so vaguely 

 termed the viscera. The anterior, the smallest, is the pectoral or thoracic ■ 

 cavity ; the posterior is named the abdomen, or abdominal cavity. The latter, 

 the only one we have now to study, is a vast oval-shaped reservoir, elongated 

 from before to behind, having for its upper wall the muscles of the sub- 

 lumbar region, inclosed below and laterally by the muscles of the inferior 

 abdominal region, bounded in front by the diaphragm, and prolonged behind 

 between the bones and membranous ligaments of the pelvis. 



The elements composing the parietes of this cavity having been already 

 described, we will confine ourselves to an examination of its interior, in 



