THE HOESE. 



103 



cus. Their arrangement is simple, as, after 

 they have formed various plexuses within 

 the thorax, in which they mutually inter- 

 change fibres, they reach the diaphragm, 

 and here are arranged as two nervous 

 branches, i. e., a superior and an inferior 

 one. The former is principally destined for 

 the fundus, whilst the latter supplies the 

 pyloric end, and sends branches off to the 

 duodenum, with one or two to the solar 

 plexus. 



The sympathetic fibres, destined for the 

 stomach, are derived from the solar plexus, 

 descending on to the viscus, in company 

 with the vessels. 



INTESTINE. 



This term is applied to that portion of 

 the alimentary canal extending between the 

 pylorus and anus, destined for the temporary 

 retention of the chymous mass, so that 

 its nutrient parts may be absorbed, whilst 

 its more solid, indigestible constituents, are 

 collected for excretion. 



The intestine in all monogastria, but es- 

 pecially in solipeda, occupies by far the 

 greatest part of the abdominal cavity. The 

 bonds of attachment to the various parts of 

 the latter are contracted by the intestine, 

 through its peritoneal investment, more 

 especially to the spine, constituting mesen- 

 ters, which I shall especially allude to when 

 describing with more detail each portion of 

 this capacious tube. 



Not only the attachments, but also the 

 shape of the intestine, vary at different parts 

 of its course, so that it has been deemed 

 necessary to divide it, either arbitrarily or at 

 natural demarcations. Thus we speak of 

 the small and large intestine, the two being 

 separated naturally by a marked change in 

 direction, size, and confirmation. 



It is also obvious that, as the situation, at- 

 tachment, and shape of each portion of the 

 intestinal canal differ, so must the relations 

 be equally distinct, and further mention of 

 them will therefore be reserved for fuller 

 exposition elsewhere. 



SMALL INTESTINE. 



This, the smallest although longest, is 

 also the fij-st portion of the intestinal tube, 

 extending from the pylorus to its sudden 

 termination into the large intestine. In it 

 the chymified mass is subjected to the modi- 

 fying influence of important secretions, 

 whereby its nutritive parts are fitted for 

 absorption by the vessels, which, for this pur- 

 pose, are arranged in this portion of the in- 

 testinal track. 



The smaU intestine has been divided into 

 three parts: this classification is, however, 

 purely conventional. Since it does not 

 recognize anatomical differences for its basis, 

 it might justly be presumed that this dis- 

 tinction of human anatomists exhibited 

 traces of imperfection, even when applied 

 to the frame of man. Such being the case, 

 it is no matter of surprise that, in referring 

 the distinction to the intestinal canal of 

 animals, the incongruities of the system 

 should be still more apparent. 



Extending from the pylorus, the first por- 

 tion is termed the duodenum, from its being 

 considered as twelve fingers' breadth in 

 length : it is, however, extended round to 

 the left side of the spine, posteriorly to the 

 anterior mesenteric artery. The middle, or 

 floating portion of gut, takes the name of 

 jejunum, and the third, or csecal portion, is 

 distinctively designated ileum. 



The duodenum forms a wide curve from 

 the pylorus round to the right, being situated 

 under the concave surface of the liver, pass- 

 ing above the transverse colon, so as to 

 attain the posterior part of the mesentery, 

 and, reaching the left side of the spine, 

 comes in contact with the colon, where it is 

 said to end in the jejunum. The duodenum 

 is fixed by the gastro-hepatic omentum to 

 the concave surface of the liver, the layers 

 of which enclose the biliary and pancreatic 

 ducts, whereby this bond of union is still 

 further strengthened. The peritoneum com- 

 ing from the right and spigelian lobes of the 

 liver, as well as from the right kidney, forms 

 a loose attachment for the duodenum by 



