26 Praetieum IV. The Mesentery. 



away the muscles carefully so as to expose the xiphisternum, noting its 

 peculiar shape and that the caudal third or fourth is cartilage. The same 

 part in man is shorter and less shapely. 



n. Remove the remaining abdominal parietes. From PI. IX 

 recognize as many as possible of the viscera by their colors, textures and 

 relative positions ; note the closeness with which they are packed, their 

 overlappings and tlie smoothness of their surfaces, covered by peritoneum. 



12. The Mesentery. The middle and caudal portion of the abdo- 

 men is chiefly occupied by the irregular coils of the SMALL INTESTINE. 

 Lift a loop of it and note that from one side extends a membrane connect- 

 ing the, intestine with the adjacent parts of the intestine and with the 

 dorsal wall of the abdomen ; this is the MESENTERY. With the tracer, 

 close to the intestine, tear the membrane slightly and note that between 

 it and the corresponding membrane from the opposite side is a little inter- 

 val ; at or near the dorsal attachment of the mesentery the two layers 

 again diverge, passing to the right and left respectively to become con- 

 tinuous with the general peritoneal lining of the abdomen. From this it 

 may be seen that the intestine lies between two layers of serosa, the ad- 

 hesion of which constitutes the mesentery ; see Anatomical Technology, 

 Fig. 78 ; compare with the thoracic septum, Plate VIII, and Pract. Ill, 

 30. 



13. The Mesenteric Vessels. The mesentery is traversed by three 

 kinds of vessels connected with the intestine : (a) ARTERIES, carrying 

 blood to it ; (d) VEINS, bringing from it blood which enters the PORTAL 

 VEIN at the liver ; (c) LACTEALS, bringing chyle to the thoracic duct. The 

 lacteals are probably invisible in ordinary alcoholic specimens, but may 

 be seen in the special preparations and in animals killed shortly after 

 taking fatty food ; Anatomical Technology, Fig. 103. Near the dorsal 

 attachment of the mesentery may be seen one or two MESENTERIC GLANDS, 

 which, like lactenls, are parts of the general LYMPHATIC SYSTEM. 



14. The Stomach and Small Intestine. Through the esophagus in- 

 flate the STOMACH, first completely to display its possible size, then mod- 

 erately, and tie the esophagus. Displace the adjacent parts so as to 

 expose the entire stomach. The esophagus opens into a larger, sub- 

 globular portion, more at the left, nearer the heart, and called the CAR- 

 DIAC region ; the more slender PYLORIC portion is flexed quite sharply on 

 the other, and is continuous with the DUODENUM or first part of the small 

 intestine. The PYLORUS, constituting the boundary between stomach and 

 intestine, may be recognized by manipulation as a distinct thickening of 

 the muscular coat ; 22 c, and Anatomical Technology, Fig 79. 



a. The three commonly accepted divisions of the small intestine, 

 DUODENUM, JEJUNUM and ILEUM, are not sharply defined although, in the 

 cat, the first may well be regarded as coextensive with the attachment of 

 the pancreas (PI. VI, D. 



15. The Spleen. This is a dark red organ lying sinistro-caudad 

 of tlie cardiac region of the stomach ; it is elongated and but loosely con- 

 nected to the stomach by a fold of peritoneum. In man tlie spleen is mas- 

 sive and its attachment is much more close. 



a. The cat's spleen varies considerably in size, but is never so compact as in man. 



b. The spleen is abundantly supplied with arteries and veins, but has no cavity or 

 excretory duct ; it is hence sometimes called a ductless gland. 



16. The Pancreas. This is a pale, lobulated organ attached quite 

 closely along the duodenum, and sending an additional portion toward 



