386 The Ducts of the Human Submaxinary Gkind 



slide (Fig. 6) this basement membrane can be distinguished at the 

 inner edge of the lumen of the duct where it appears as a delicate 

 irregular line. The slight clear area just outside of the basement mem- 

 brane is caused by the spaces left by the elastic tissue, the fibres of 

 which have been entirelj'' dissolved from the specimens by the action 

 of the enzyme. The connective tissue embracing the duct is now dis- 

 tinctly fasciculated and arranged so that its bundles seem, at the same 

 time, to give the greatest strength and elasticity to that part of the 

 duct. Numerous connective tissne corpuscles, endothelial cells lining 

 the lymph spaces and capillaries, can be seen in the frame-work just 

 about the interlobnlar ducts, the vasa comites cut in cross-section are 

 also evident. Specimens stained with Weigert's elastic tissue method 

 (Fig. 7) show external to the basement membrane, a dense, deeply- 

 staining, elastic membrane, composed of interlacing elastic, fibres which 

 entirely embraces the duct and appears, in these specimens, like an 

 irregular black line *just external to the epithelium. ISTumerous elastic 

 fibres having a concentric lamellar arrangement are found outside 

 of the main elastic membrane. Some fibres connect the cliiferent con- 

 centric elastic lamellas, while others, variously arranged, appear to be 

 extensively distributed throughout the entire interspace. Ducts of the 

 next higher order, namely the sublobular ducts (Figs. 4 and 8), are 

 likewise embraced by the coiniective tissue of the sublobular spaces, but 

 this is now greatly diminished in amount. The sublobular ducts like 

 those of the lower orders are lined by a double layer of epithelial cells. 

 The cells of the inner columnar layer are much lower than those of 

 the corresponding layer of interlobular ducts or ducts of the first 

 order. The nuclei are more nearly spherical, the cytoplasm is some- 

 what diminished in quantity and appears slightly more granular. These 

 cells are likewise slightly smaller and more compact than those of the 

 corresponding layer of the larger ducts, the basement membranes are 

 clearly marked and the connective tissue has the same characteristic 

 fasciculated appearance noted in the larger interspaces, except that the 

 fasciculi are much smaller and more compactly arranged. Connective 

 tissue cells, endothelial cells and blood-vessels are also found in these 

 spaces bearing ostensibly the same relation to the ducts and connective 

 tissue which we have observed about the larger branches. 



The elastica of the sublobular ducts is very well marked, forming a 

 thick mesh-work of anastomosing and interlacing fibrils lying just be- 

 neath the membrana propria. As in the larger ducts there is the same 

 concentric arrangement of the elastic lamella^, the latter alternating 

 Avith layers made of white fibrous tissue and reticulum with numerous 



