Joseph Marshall Flint 2?3 



small lobe or prolongation, however, is usually observed passing beneath 

 the M. niylohyoideus with the D. subniaxillaris in rather intimate asso- 

 ciation with it. This portion may be completely free from the major 

 part of the gland forming an aberrant lobe, the duct of which joins the 

 D. subniaxillaris at a point somewhat below the hilus. 



In taking up the description of the course of the secretory channels 

 within the organ it is perhaps best for the sake of clearness to begin 

 with the main duct aud then proceed through its complex ramifications 

 to the alveoli, although this course is opposite that taken by the secre- 

 tion. On the other hand from an embryological point of view, it is, of 

 course, obvious that in adopting this method of description we follow 

 the path taken by the gland in its development. In discussing the 

 course of the ducts it will be necessary to refer, from time to time, to 

 certain facts concerning their development, accordingly, at the outset, 

 it may be well to recapitulate briefly certain details of the organogenesis 

 of the siibmaxillary which are to form the substance of a later com- 

 munciation. The first anlage consists of a spur from the epithelium ot 

 the mouth which marks the beginning of the duct. This anlage is a 

 solid cylindrical column of cells which grows and finally begins to 

 branch. The branching portion becomes encapsidated and indicates the 

 primitive form of the organ as we know it in adult life. At this stage 

 it is composed of a blastema of branching nucleated cells in which the 

 growing ducts are embedded. The growth at this stage is chiefly apical 

 and the branches of the simple little tree which later is transformed 

 into the major ducts of the gland terminate in little buds or swellings 

 that form the growing points at the apices. As the gland develops 

 these simple cell columns divide and ramify and become more complex 

 until, after giving rise to the ducts of the first order, interlobular, 

 lobular and intercalary ducts, they produce finally the alveoli and 

 secreting elements of the gland. In their growth, the ducts and their 

 accompanying vessels are surrounded by strands of connective tissue 

 wliich form later the interlobular spaces. At the time when the rami- 

 fication has proceeded to a certain point, the growing ends become sur- 

 rounded by a fine capsule or membrane which marks the initial forma- 

 tion of the lobule and its membrana limitans. This membrane is at- 

 tached to the growing duct at the future site of the lobular hilus and 

 forms the one firm point of attachment of the lobule. Within this 

 membrane, the intralobular ducts and alveoli are developed. At first 

 the lobules are comparatively free but later become, as they increase 

 in size, closely packed together, forming the irregular polygonal shapes 

 observed in adult life. It is in this way that the limiting membranes of 



