XVII.] INTESTINE. BILE. PANCEEATIC JUICE. 183 



6. Examine sections of a small intestine in which 

 the blood-vessels have been injected, and note 

 the capillary network round the glands of Lie- 

 berkiihn, and the small artery running up each 

 villus and dividing into a capillary network just 

 below the cells. 



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

 next day' kill the frog, remove the stomach and 

 intestine, pin the tube out on cork, cut it open 

 along its whole length, and gently wash it 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. Teaze 

 out a small piece of the opaque white mucous 

 membrane in normal salt solution; the epithe- 

 lium cells are crowded with fat globules, scarcely 

 anything but these being visible. 



Fat is absorbed by the oeUs 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 



^ 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, An 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. For hardening the intestine cp. § 2. p. 33. 



