396 THE PAXCREAS. 



the inner curved border of the duodenum, is attached more particuharly 

 to the descending and transverse portion of that intestine, encroach- 

 ing slightly on both the anterior and posterior surface. The ductus 

 communis choledochus passes down behind the head of the pancreas, 

 and is generally received into a groove or canal in its substance. 



Structure. — The pancreas belongs to the class of compound race- 

 mose glands. In its general characters, and also in its intimate structure 

 it closely resembles the salivary glands, to the description of the minute 

 structure of which the reader is referred (p. 339). It is somewhat 

 looser and softer in its texture than those organs, the lobes and lobules 

 being less compactly arranged. 



The alveolar cells differ from those of the submaxillary gland in not containing- 

 mucus, resembling in this respect the cells of the parotid : moreover, the 

 columnar cells of the ducts appear to be devoid of the striated base seen in 

 those of the submaxillary, and the ducts themselves have an irregular, angular 

 shape : but in all essential points of structure, and in the distribution of the 

 vessels and nerves, the two glands, as far as is known, entirely agree. 



The principal excretory duct (fig. 282, o), called the pancreatic duct 

 or canal ofWirsung (by whom it was discovered in the human subject 

 in 1C42), runs through the entire length of the gland, from left to 

 right, buried completely in its substance, and placed rather nearer its 

 lower than its upper border. Commencing by the union of the small 

 ducts derived from the groups of lobules composing the tail of the 

 pancreas, and receiving in succession at various angles, and from all 

 sides, the ducts from the body of the gland, the canal of Wirsung in- 

 creases in size as it advances towards tlie head of the pancreas, where, 

 amongst other large branches, it is usually joined by one derived from 

 that portion of the gland called the lesser pancreas. Curving slightly 

 downwards, the pancreatic duct then comes into contact with the left 

 side of the ductus communis choledochus, which it accompanies to the 

 back part of the descending portion of the duodenum. Here the two 

 ducts, placed side by side, pass very obliquely through the muscular and 

 areolar coats of the intestine, and terminate, as already described, 

 on its internal mucous surface, by a common orifice, situated at 

 the junction of the descending and horizontal portions of the duo- 

 denum, between three and four inches below the pylorus. The pan- 

 creatic duct, with its branches, is readily distinguished from the glandu- 

 lar substance, by tlie very white appearance of its thin fibrous walls. 

 Its widest part, near the duodenum, is from 1 line to lA line in diameter, 

 or nearly the size of an ordinary quill ; but it may be easily distended 

 bevond that size. It is lined by a remarkably thin and smooth mucous 

 membrane, which -near the termination of the duct occasionally presents 

 a few scattered recesses. 



Varieties. — Sometimes the duct is double up to its point of entrance into the 

 duodenum ; and a still further deviation from the ordinary condition is not 

 unfrequently observed, in which there is a .stq)fh/iitrnfiirij duct, derived from the 

 lesser pancreas or some part of the head of the gland, opening into the duodenum 

 by a distinct orifice, at a distance of an inch or more from the termination of 

 the principal duct. It sometimes occurs that the pancreatic duct and the common 

 bile duct open separately into the duodenum. 



Vessels and Nerves. — Like the salivary glands, the pancreas receives its 

 blood-vessels at numerous points. Its arteries are derived from the splenic and 

 from the superior and inferior pancreatico-duodenal branches of the hepatic and 



