THE DIGESTIVE ORGANS. 



141 



vascular areolar tissue, and broader bands of that tissue divide the 

 whole gland into small lobes and these again into still smaller 

 lobules (Fig. 25). 



The ducts of the salivary glands are lined with columnar or pyram- 

 idal epithelial cells, the attached ends of which often show a stria- 



Fig. 120. 



Part of a cross-section of the oesophagus of a dog. (Bohm and Davidoff.) a, mucous mem- 

 brane ; b, submucous coat ; c, muscular coat ; d, fibrous coat ; e, stratified epithelium ; /, 

 subepithelial areolar tissue (sometimes called the " tunica propria " of the mucous mem- 

 brane) ; g, muscularis mucosa? ; h, areolar tissue of the submucosa, containing the chief 

 branches of the arterial and venous vessels ; i, internal, encircling layer of the muscular 

 coat. It is the contraction of this coat that has caused a longitudinal wrinkling of the 

 mucous membrane. One of those folds is completely and two are partially shown, j, 

 external, longitudinal layer of the muscular coat ; k, areolar tissue forming the external 

 coat and connecting the oesophagus with neighboring structures. A few large vessels 

 entering the oesophagus are represented in this coat. 



tion perpendicular to the surface of the basement-membrane (Fig. 

 119). 



The nerves ramify in the interlobular areolar tissue and send 

 delicate, non-medullated fibres through the basement-membrane to 

 be distributed upon and between the epithelial cells. Occasionally 

 small ganglia are seen upon the larger nerves. 



