Joseph Marshall Flint 



379 



off the indivicliial branches. There is often considerable tortuosity 

 observed in their course (Fig. 2). They run between the lobules em- 

 bedded in the thick fasciculated connective tissue of the interlobular 

 spaces and are accompanied by the vasa comites. From these occasional 

 lobular ducts are derived. As a rule, however, they break up into the 

 sublobular ducts which leave the interlobular ducts at sharp angles and 

 ramify among the lobules. They are called sublobular because it is 

 from them or their chief divisions that the 

 great majority of lobular ducts are derived. 

 The latter are proportionately longer than 

 ducts in other parts of the system and pass 

 Anthout dividing through the hilus of the lob- 

 ule to ramify in the substance of the lobule 

 itself. The position of the lobular ducts in 

 corrosions can be identified by comparing them 

 Avith the ducts of the same nature in digested 

 preparations and sections of injected glands, 

 the size of the ducts as well as their course 

 corresponding perfectly in preparations made 

 by both methods. When viewed under the 

 stereoscopic microscope the lobular ducts ram- 

 ify through three or four divisions which often 

 follow in such close succession that the gen- 

 eral rule of dichotomy seems to be violated, 

 the case, for two complete trunks can always 

 Careful study, however, shows that this is not 

 be found after a division has taken ■ place 

 although tli^y may occur very close together. 

 The division is rapid so that the terminal 



ducts are thoroughly distributed throughout the lobule. These intra- 

 lobular duets which are synonymous with the salivary tubes of Pfluger, 

 pass towards the center of the lobules and then radiate towards the 

 periphery without ever quite reaching it, owing to the layers of acini 

 which are interposed between them and the limiting membrane. 



When the terminal branches of the intralobular ducts are reached 

 the law of dichotomy is often violated; branches occur more frequently 

 and more abru|)tly, three or four sometimes arising at the same level. 

 These divisions are the intracalary ducts which are usually about one- 

 third the diameter of the terminal intralobular ducts in injected prepa- 

 rations. They run at obtuse angles from the ducts from which they 

 spring. These intercalary ducts are of variable length and often 



Fig. 3. Celloidin corrosion of 

 terminal ducts and alveoJar 

 amimUa:. Magnified about 

 115 diameters- The main 

 trunk in this preparation 

 represents the end of one of 

 the intralobular ducts which 

 exhausts Itself In giving oCC 

 the intercalary branches. 

 These may be divided once 

 or twice and then terminate 

 in the alveolar ampull;e 

 which look like little o\oid 

 or pear-shaped ends of the 

 corrosions. 



J'— intralobular duct. 



G— intercalary duct. 



If— alveolar ampulla?. 



