164 



JOHN SUNDWALL 



ducts — (a) dichotomously or (b) the main interlobular ducts 

 continuing as such for some distance with smaller intralobular 

 ducts taking origin at ^'arious levels. 



The intralobular ducts have an extensive ramification as well. 

 The branching is chiefly of the dichotomous type although 

 trichotomous branching is seen. The branches are as a rule 

 very unequal in calibre. Each lobule as a rule contains many 

 of these ducts of unequal sizes. At various levels in the course 

 of these ducts, nodular enlargements are seen. Frequently 

 the ducts are seen to terminate in nodular enlargements. It is 

 somewhat difficult to force the injection mass beyond these 

 nodules. However, after careful and repeated trials it is possible 

 to force it (celloidin is preferable) to the alveoli or tubules and 



Fig. 6a Corrosion cast of main duct with branches. Drawing, binociihir, 

 somewhat diagrammatic. M, main duct; P, primary duct; 7, Interlobular duct; 

 /', intralobular duct; /", intercalary duct; T, tubules. 



when this is accomplished it is seen that these nodules mark the 

 exits of the intercalary or junctional duct. 



The lumina of the intercalary ducts are exceedingly fine and 

 threadlike as represented by the celloidin or celluloid cast. As 

 a rule two or three of these ducts leave each nodule at right angles 

 to the intralobular ducts and terminate in the tubules. Fre- 

 quently they are seen to undergo dichotomous and in some 

 instances trichotomous branching before so terminating. From 

 two to three tubules mark the termination of the intercalary 

 duct. 



The entire duct system belonging to one main duct forms an 

 elongated gland (fig. 6 a). Generally the primary duct leaves 

 the main duct at an acute angle. The branching of the secondary 



