THE SALIVARY GLANDS. 



10.") 



albuminous in nature, and probably yield to the secretion of the 

 inland its ferment (ptyalin) and perhaps its albumin. The granular 

 substance within the cell is not the ferment, but the ferment is formed 

 from it when the secretion is poured out. Hence it has been termed 

 '.'t/uwyrn (mother of ferment). The outer part of each cell becomes 

 clear and free from granules after secretion (fig. 194). 



The largest ducts have a wall of connective tissue outside the base- 

 ment-membrane, and also a few plain muscular cells. The blood-vessels 

 of the salivary gland form a capillary network around each alveolus. 

 The lymphatics commence in the form of lacunar vessels encircling the 

 .alveoli. The nerve-fibres, which are derived both from the cerebro- 

 spinal nerves and from the sympathetic, have not been satisfactorily 

 traced to their termination, but they probably become connected with 

 the alveolar cells. 



THE PHARYNX AND (ESOPHAGUS. 



The pharynx is composed of a fibrous membrane, which is encircled 

 by striated muscles, the constrictors, and lined by mucous membrane. 

 The mucous membrane is lined in the upper part of the pharynx and 





FIG. 196. SECTION OF THE HUMAN (ESOPHAGUS. (From a sketch by V. Horsley.) 



The section is transverse, and from near the middle of the gullet, a, fibrous covering ; b, 

 divided fibres of the longitudinal muscular coat ; c, transverse muscular fibres ; d, sub- 

 mucous or areolar layer; e, muscularis mucosse ; /, papillae of mucous membrane ; g, lami- 

 nated epithelial lining ; h, mucous gland ; i, gland duct ; m', striated muscular fibres in 

 section. 



