1734 



HUMAN ANATOMY. 



it may extend across this surface, or rest on the basal one. There are two horizon- 

 tal grooves on the posterior surface. The lower, which is the longer and deeper, is 

 caused by the splenic vein. It extends from the left end to the groove for the portal 

 vein, inclining to the lower border as it approaches it. A smaller groove for the 

 splenic artery lies above the former from the left to near the aorta. 



The antero-superior surface, the largest of the three, slants downward and 

 forward, presenting a concavity which forms a part of the stomach-bed. It is on 

 the average some 4 cm. broad, but may exceed 5 cm. There is often a swelling — the 

 omental tuberosity (tuber omentale) — to the left of the neck opposite the aorta. This 

 is behind the lower end of the vertical part of the lesser curvature of the stomach, 

 and is in contact with that organ rather than with the omentum. 



The inferior surface, the smallest, rarely as much as 2 cm. in breadth, 

 rests on the lower layer of the transverse mesocolon. It is rounded and irregular, 

 except where it lies above the duodeno-jejunal fold, -where it is smooth and concave. 

 To the right of this it is grooved by the superior mesenteric artery. 



The borders at which the surfaces meet call for no special description beyond 

 that both the inferior ones are grooved by the superior mesenteric artery and the 

 upper by the cceliac axis. 



Structure. — While agreeing in its general structure with other serous salivary 

 glands, as the parotid, the pancreas differs in certain particulars. The most im- 



FiG. 1462. 



Section of pancreas under low magnification, showing general arrangement of lobules. X 30. 



portant of these are the tubular, rather than saccular, form of the alveoli, the marked 

 differentiation of a granular zone in the protoplasm of the secreting cells, the absence 

 of specialized intralobular ducts, and the presence of the islands of Langerhans. 



The chief pancreatic duct gives of? numerous lateral interlobular branches which 

 are lined with a single layer of columnar epithelium, about .006 mm. in height, the 

 direct continuation of that clothing the large ducts, in which the cells are from two 

 to three times as tall. The canals springing from the interlobular ducts after enter- 

 ing the lobules possess a layer of flattened epithelial plates some .012 mm. long by 

 .003 mm. high, and correspond to the intercalated or intermediate ducts. The in- 

 tralobular canals being wanting, the relatively long intermediate ducts pass directly 

 into the tubular alveoli, within which their attenuated epithelium protrudes as the 

 centro-acinal cells. The relation of the latter to the usual glandular elements lining 

 the alveolus is peculiar, the thinned-out and spindle duct-cells being surrounded ex- 

 ternally by the secreting cells. 



The tubular alveoli of the gland, often tortuous and sometimes divided,, possess 

 a well-defined membrana propria against which lie the secreting cells. The latter 



