SECRETION. 



243 



Brunner. These glands resemble closely in arrangement those of the pyloric 

 end of the stomach, with the exception that the tubular duct is more branched. 

 The secreting cells are similar to those of the pyloric glands of the stomach. 

 Little is known of their secretion. According to some authors it contains 

 pepsin. The amount of secretion furnished by these glands would seem to 

 be too small to be of great importance in digestion. Throughout the length 



Fig. 64.— Glands of the fundus (dog) : A and A 1 , during hunger, resting condition ; />, during the tir-t 

 stage of digestion : ''and />, the second stage of digestion, showing the diminution in the Bize of the 

 "chief" or central cells (after Heidenhain). 



of the small and large intestine the well-known crypts of Lieberkiihn 

 are found. These structures resemble the gastric glands in general appear- 

 ance, but not in the character of the epithelium. The epithelium lining the 

 crypts is of t\\<> varieties — the goblet cells, whose function h to form mucus, 

 and columnar cells with a characteristic striated border. The changes in the 

 goblet cells during secretion and the probability of a relationship between them 

 and the neighboring epithelial cells has been discussed (see p. 216). 

 Whether or not the crypts form a definite secretion has Ween much debated. 

 Physiologists are accustomed to speak of an intestinal juice, " succus entericus," 

 as being formed by the glands of Lieberkiihn, but practically uothing is known 

 as to the mechanism of the secretion. The succus entericus itself, however it 

 may be formed, can be collected by isolating small loops of the intestine and 



