i 



—a 



290 The Ducts of the Human Submaxillary Gland 



lobular ducts for some little distance into the lobule, but these cases are 

 exceptional. Both the interlobular and intercalary ducts are provided 

 with basement membranes which differ so little from the membranas 

 proprias of the acini that it is usually necessary to orient them in di- 

 gested specimens in order to distinguish ducts from alveoli (Fig. 6). 

 These basement membranes consist of a delicate network of interlacing 

 fibrils of reticulum which appear in sections cut tangentially to the 

 membrane as a cross-hatch or mesh-work of interlacing fibrils which 

 are only visible with the immersion lens. When viewed with the lower 

 powers the membrana propria usually appears loractically homogeneous. 



At the point of termination of 

 f the intercalary ducts- a slight 



'A constriction is noted, in corro- 



^ sions, just as they widen into 



/ , ^ «; the ampulla. In sections the 



flattened epithelium at this 

 point changes abruptly into the 

 p '' »Y^ "'^ regular epithelium of the alveo- 



■ \%. • . . * lus. In sections cut in the right 



^t.!j*J^ plane it is possible not only to 



see the intercalary duct termi- 



Fig. 9. Terminal intralobular duct, intercalary natinff in the alveoli but to make 

 ciuct, and ^roup of mucous alvedli sliownig' the c' 



Sl^'^oi^^T,*^^^?*^^^^*-. ^"'^(^'\^"^iV'='^*l'='7'o^}''y"^- out the little ovoid spaces form- 



Stained by Henson s method. Maynitied 300 dia- -i^ 



^^^vf^v- .• * +V, *• • 1, +1 * +1, ins: the ampulla as well (Fig. 



The direction of the section is such that the f-^ i \ o 



intralobular duct is cut In cross section and the 9)_ ^^ ^ -^^q hoWCVer, the 

 intercalary duct tang-entiallj' so that one does not '' ' ' 



see its lumen. Inasmuch as the alveoli are not \m\QX borders of the CClls of 

 collapsed, the alveolar ampullae are distinctly 



''''^''- «- intralobular duct. ^""^^ alveolar epithelium are in 



c-ah*eoiar'a'^mpuiia close approximation so that in 



the collapsed state of the alveo- 

 lus only a small chink is left between them. About the serous alveoli 

 there are only a few occasional elastic fibres; about the mucous 

 alveoli, however, these fibres are numerous, as has been shown by 

 Livini.' Their nature and relations, however, Livini did not de- 

 scribe. It appears that these fibres, which under the lower power of 

 the lens look homogeneous, are in reality very delicate elastic mem- 

 branes made up of an intertwining and interlacing mesh-work of fibres 

 which have a reticulated appearance similar to that of the regular mem- 

 brana propria. This elastic membrane appears to lie outside of the 

 regular membrana propria of the mucous alveoli. As Livini pointed 



8 Livini : Monitore Zoologico Italiano, vol. x, 1S99. 



