i8o ANIMAL BIOLOGY. [Parti. 



cell being much reduced in size. After a period of secretion 

 the cells decrease in size, so that the lumen (or cavity), which 

 was before almost or quite obliterated, becomes obvious. The 

 cell-contents are much less granular, and the granules are re- 

 stricted to that part which lies nearest the lumen. The pro- 

 toplasm is relatively increased in amount, and the nucleus, 

 before disc-shaped and seen with difficulty, becomes more 

 clearly visible, and spherical. 



The gastric glands are of two kinds, cardiac and pyloric. The 

 cardiac glands, which are developed in all parts of the stomach 

 except the pylorus, are simple tubes, of which two or three may 

 open into the same duct. They are lined with epithelial cells, 

 columnar and transparent in the body of the gland, more 

 cubical in the neck. Between these epithelial cells and the 

 supporting membrane is a discontinuous layer of large granular 

 oval cells (parietal cells). The pyloric glands have longer ducts 

 and are more curved. The epithelial cells of the body of the 

 gland are cubical, and resemble those in the neck of the cardiac 

 gland. There are no parietal cells. 



Of the intestinal glands, Brunner's are practically continuous 

 with the pyloric glands, but are more decidedly branched, almost 

 racemose, in character. They are confined to the duodenum. 

 But throughout the whole of both small and large intestine there 

 are great numbers of the simple tubular glands (or crypts) of 

 Lieberkuhn which are lined with columnar epithelium. 



There remain the pancreas and liver. Of these the pancreas 

 is a racemose gland resembling the salivary glands in structure, 

 the lobules containing the dilated ends of the branched tubes. 

 The liver has a different structure, each lobule containing a 

 reticulum of bile canaliculi. Each lobule has, moreover, a double 

 blood-supply. It receives arterial blood from the aorta by the 

 hepatic artery : it receives venous blood from the alimentary 

 canal by the portal vein, The blood is carried off by the 

 hepatic veins to the post-cavaL Traced backwards each hepatic 

 vein is found to result from the union of a great number of 

 factors, the small hepatic veins, and these again receive yet 

 smaller factors, the sub-lobular veins. Around these sub-lobular 



