THE INTESTINES AND INTESTINAL DIGESTION 107 



The mucous coat of both large and small intestines also 

 resembles that of the stomach in that it consists chiefly of glands. 



But the glands are of various kinds ; some are tubular, and 

 arranged parallel with each other. Others (Peye*>s glands} are 

 somewhat globular or ovoid in form, and are distributed singly 

 (solitary} or in groups (Peyev>s patches}. Others, again, are 

 minutely lobulated (Brunnet>s glands}, and are so large as to be 

 visible to the naked eye. 



The ducts of all these glands (excepting the PcyeSs glands, 

 which have no ducts) open on the internal surface of the intestines 

 and thus pour their secretions into the alimentary canal. 



Fig. 1 02. A Portion of 

 the Small Intestine 

 laid open to show the 

 Folds of the Mucous 

 Membrane (Valvulse 

 Conniventes). 



Fig. 103. A Small Por- 

 tion of the Mucous 

 Membrane of the 

 Small Intestine. 



Magnified 12 dia- 

 meters. 



a., Payer's glands, surrounded 

 by tubular glands ; b, villi ; 

 c, openings of the tubular 

 glands. 



The nature of the secretions of these glands is not well under- 

 stood. Some of them probably secrete mucus only ; others are sup- 

 posed to resemble the salivary glands and the pancreas in function. 



The interior surface of the small intestine is covered also with 

 a multitude of minute projections called villi (Lat. shaggy hair) 

 which give the surface a fine velvety appearance. These, however, 

 will be described in our next lesson, as they are engaged in the 

 absorption of nutritious matter rather than in the digestion of 

 food. 



When the partially digested food passes from the stomach, 

 through the pylorus, it almost immediately mingles with two very 

 important digestive fluids, called the bile and the pancreatic fluid 



