404 STRUCTURE OF STOMACH. [BOOK IL 



is continuous with the general epithelial lining of the canal) divides, 

 dichotomously or otherwise, into secondary ducts, which again divide 

 into smaller ducts, and this division may be repeated again and 

 again ; ultimately however each duct ends in a part in which the 

 epithelium takes on secreting characters, and such terminal portions 

 of ducts which are generally wider, more swollen as it were, than 

 the ducts leading to them and not infrequently flask-shaped, are 

 spoken of as alveoli. These alveoli, especially when flask-shaped, 

 bear a certain, though by no means close, resemblance to the indi- 

 vidual berries on a bunch of grapes, the ducts being the branching 

 stalks ; hence these compound glands are spoken of as " racemose." 

 Sometimes the gland in dividing spreads out loosely over a wide 

 surface, that is to say, is ' diffuse ' ; sometimes the ducts and alveoli 

 with all the connective tissue, blood vessels, &c., belonging to them 

 are bound up tightly into a more or less globular mass, that is to 

 say, form a ' compact ' gland. 



Glands in fact vary widely in size, form and complexity, but 

 they all have the one feature in common that they, being involutions 

 of the mucous membrane, consist of a wall of vascular connective 

 tissue lined by epithelium, and in the majority of glands there is 

 a distinction in the characters of the epithelium between a terminal 

 secreting portion and a proximal conducting portion. 



Where, as in the stomach and intestine, a number of com- 

 paratively simple glands are closely packed together side by side, 

 the whole mucous membrane acquires proportionately increased 

 thickness ; instead of being an attenuated sheet formed of a single 

 layer of cells on a thin connective tissue basis it becomes a mass 

 whose thickness is determined by the length of the glands. 



It may be added that generally but not always the gland in 

 its whole length lies above or outside the muscularis mucosse, so 

 that when a vertical section is made of a mucous membrane the 

 muscularis mucosae is seen running in an even line at some little 

 distance below the thick layer which is presented by the longitu- 

 dinal sections of the glands. 



Bearing in mind these general characters of the alimentary 

 canal and its glands we may now proceed to study some of its 

 special characters, and it will be convenient to begin with the 

 structure of the stomach. 



Structure of the Stomach. 



210. The stomach in its structure follows the general plan 

 just described, and consists of a muscular coat and a mucous 

 membrane separated from each other by loose submucous con- 

 nective tissue. The muscular coat, which has considerable thick- 

 ness, consists of an outer somewhat thick longitudinal coat and an 

 inner still thicker circular coat, the innermost bundles of which 

 take an oblique direction and form a more or less distinct thin 



