176 PRACTICAL HISTOLOGY [XXII 



capillary network round the glands of Lieberktihn, and 

 the small artery running up each villus and dividing 

 into a capillary network just below the epithelium. 

 The submucous tissue contains rather large vessels 

 which give branches both to the mucous and the 

 muscular coat. 



6. Section of frog's intestine after feeding with fat 

 (osmic acid). The columnar cells contain numerous fat 

 globules of various size, the hyaline border is free from 

 fat. 



7. Feed a frog with a small piece of bacon ; on the next 

 day 1 kill the frog, remove the stomach and intestine, pin the 

 tube out on cork, cut it open, and gently wash with salt solution. 



Note that the mucous membrane of the stomach has a 

 yellowish semi-transparent look, whilst the mucous membrane 

 of the intestine is of an opaque white this is more marked in 

 the upper than in the lower part of the intestine ; the rectum is 

 greyish and semi-transparent. Tease out a small piece of the 

 opaque white mucous membrane in normal salt solution ; the 

 epithelium cells are crowded with fat globules, scarcely anything 

 but these being visible, ^at is absorbed by the cells of the 

 small intestine, and is absorbed little or not at all by the cells 

 of the stomach. 



8. Pin out pieces of the intestine ; place some in 75 p.c. 

 alcohol for an hour, and then in strong spirit ; place others in 

 osmic acid 1 p.c. for half-an-hour, wash and place in 75 p.c. 

 alcohol. 



In sections of these pieces note that there are no villi and no 



1 The difference in the tint of the stomach and intestine is still 

 more obvious if the frog be fed again after two days and killed on the 

 subsequent day. The frog is fed by placing the piece of fat in the 

 upper part of the oesophagus, the fat is then usually swallowed at 

 once. 



