THE ESSENTIALS OF HISTOLOGY. 



FIG. 189. DIAGRAM OF THE CONSTRUCTION OK A LOBULE OF A TUBULO-RACEMOSK 

 (ACINO-TUBULAR) MUCOUS GLAND. (Kolliker.) 



, duct ; b, a branch of the duct ; c, alveoli as they lie together in the gland ; d, the same 

 separated, showing their connection as an irregular tube. 



FIG. 190. MEMBRANA PROPRIA OF TWO ALVEOLI ISOLATED. (Heidenhain. ) 



The preparation is taken from the orbital gland of the dog, which is similar in structure to 

 a mucous salivary gland. 



FIG. 191. SECTION OF THE SUBMAXILLARY GLAND OF THE DOG, SHOWING THE 

 COMMENCEMENT OF A DUCT IN THE ALVEOLI. (Magnified 425 diameters.) 



a, one of the alveoli, several of which are in the section shown grouped around the 

 commencement of the duct d' ; a', an alveolus, not opened by the section ; b, basement- 

 membrane in section ; c, interstitial connective tissue of the gland ; d, section of a duct 

 which has passed away from the alveoli, and is now lined with characteristically striated 

 columnar cells ; s, semilunar group of darkly stained cells at the periphery of an alveolus. 



