THE ORGANS ANNEXED TO ABDOMINAL DIGESTIVE CANAL. 503 



Excretory apparatus. — The pancreas has two excretory ducts — a principal, 

 described by "Wirsung, whose name it bears, and an accessory. The duct of 

 Wirsimg, lodged in the substance of the gland, but nearer the superior than the 

 inferior face, at first comprises two or three thick branches, which soon unite to 

 form a single trunk that emerges from the pancreas by the left extremity of the 

 organ. Larger than the ductus choledochus, it opens, as already stated, at 

 the same part of the duodenal surface. The accessory or azygos duct {ductus 

 vancreaticus minor) is much smaller ; it leaves the principal trunk, receives some 

 branches in its passage, and opens alone into the small intestine, directly opposite 

 the duct of Wirsung. 



The ductus choledochus and the duct of "Wirsung do not pass directly through 

 the wall of the intestine, but obliquely, like the entrance of the ureters into the 

 bladder. They open in the middle of a circular valve — the ampulla of Vater. 

 This ampulla is limited by a thick primary mucous fold, and within this is a 

 second — thinner — beneath which the ductus choledochus opens ; at the bottom of 

 the space circumscribed by this second fold, beneath a free mucous lip, is seen 

 the duct of Wirsung. Such is the arrangement of the ampulla of Vater in the 

 Horse. 



Functions. — From the researches of Bernard, it appears established that 

 the fluid secreted by the pancreas emulsifies fatty matters, and renders them 

 absorbable. 



3. The Spleen (Fig. 299). 



The spleen differs from glands, not only in the absence of an excretory duct, 

 but also in the other details of its organization. It has been considered as a 

 vascular gland, the uses of which are not yet determined in a precise manner. 



Situation. — It is situated in the diaphragmatic region, close to the left 

 hypochondriac, and appears as if suspended in the sublumbar region, as well as 

 at the great curvature of the stomach. 



Foryn — Direction — Relations. — The spleen is falciform, and directed obliquely 

 downwards and backwards. It has tivo faces, tvw borders, and a point. 



The external face is in relation with the muscular portion of the diaphragm, 

 and is moulded to it. The internal, slightly concave, touches the large colon ; it 

 has sometimes a small lobule, or offers traces of lobulation. The posterior border 

 is convex, thin, and sharp. The anterior, thicker, concave, and bevelled at the 

 expense of the internal face, is channeled by a slight longitudinal fissure (or 

 hilus) that lodges the splenic vessels and nerves ; it receives the insertion of the 

 great mesentery, by which it is attached to the greater curvature of the stomach. 

 The base, or superior extremity, is thick and wide, and is related to the left 

 kidney and the corresponding extremity of the pancreas ; it shows the insertion 

 of the suspensory ligament. The point, or inferior extremity, is smooth and 

 thin. 



Weight. — The average weight is 32 ounces ; but it is sometimes of enormous 

 dimensions — as much as three or four times its normal volume. 



Mode of attachment. — The spleen is a floating organ, the displacements of 

 which are limited by a suspensory ligament, and the great (or gastro-splenic) 

 omentum. The first is a peritoneal fold which proceeds from the anterior border 

 of the left kidney and the sublumbar wall, and is strengthened by the elastic 

 fibrous tissue comprised between its two layers. It is fixed to the base of the 

 spleen, and is confounded, inwardly, with the great omentum. The latter is 



