416 PHYSIOLOGY OF THE DOMESTIC ANIMALS. 



rabbit, by the action of at r opine and by stimulation of the sensory 



nerves. 



The pressure under which the pancreatic juice is secreted is not 

 much higher than that of the bile, amounting only to about seventeen 

 millimeters of mercury. 



III. THE INTESTINAL JUICE. In addition to the fluids poured out by 

 the liver and the pancreas, the walls of the small intestine are also 

 abundantly supplied with glands, which pour out a secretion which 

 possesses a certain digestive value. The largest amount of this fluid is 

 poured out by the so-called duodenal follicles, or glands of Lieberkiihn, 

 to which is added the scanty secretion of the small, convoluted, tubular 

 Br miner's glands. The latter are morphologically identical with the 

 glands of the pylorus and stomach, and their cells are turbid and small 

 during hunger, while during digestion they are large and clear. In the 

 sheep the Brnnner's glands form a continuous laj^er and their walls pour 

 out a fluid containing mucin and ferments which possess the power of 

 dissolving proteids and of converting starch into sugar. Any data as to 

 the action of the secretion formed by these glands are, however, obtained 

 with the greatest difficulty on account of the smallness of the glands and 

 impossibility of isolating their secretion ; consequently, the greatest 

 uncertainty surrounds their functions. 



The glands of Lieberkiihn are small, tubular glands set vertically in 

 the mucous membrane and are lined by c}dindrical epithelial cells, among 

 which numerous goblet, mucous cells may be found. These cells, appar- 

 ently, are the main source of intestinal juice, the so-called succus entericus. 



Yarious methods have been proposed for obtaining the fluid poured 

 out by these glands. Thiry's method was to withdraw a loop of small 

 intestine from the abdomen, and excise a portion several inches in 

 length, leaving its blood supply intact, and then restoring the continuity 

 of the intestine by stitching together the ends above and below where 

 the excised portion had been removed. One end of the excised portion 

 was then closed by stitches, while the other extremity was kept open 

 and stitched into the abdominal wall. By this means a small portion of 

 the small intestine was isolated, and as it communicated with the exterior 

 the secretion which it formed could be readily collected. Yella improved 

 the method employed by Thiry by leaving both ; ends of the isolated 

 portion open, after restoring the continuity of the bowel, and stitching 

 them to the abdominal wound. It is evident that after this operation 

 the small intestine cannot be regarded as being in its normal condition, 

 for it is entirely removed from contact with the secretions and chyme, 

 and undergoes a considerable amount of atrophy ; and although its 

 secretion is not contaminated by any other digestive fluid, it cannot 

 be regarded as being in a normal condition. 



