428 The Submaxillary Gland 
subdivided into ultimate lobules, so that at their bases anastomoses may 
occur between the alveolar capillaries of the peripheral portions of adja- 
cent ultimate lobules. 
ANGIOGENSIS. 
Chievitz* has shown that the submaxillary gland develops as a bud 
from the buccal epithelium. This’ grows backward toward the angle 
of the mandible and there begins a dendronal branching that marks 
the anlage of the submaxillary gland. Owing to the difficulty in inject- 
ing very early embryos, a study of the relationship between vessels 
and cells can best be made in stained sections. The submaxillary gland 
is shown in a simple form in pigs represented by about 33 centi- 
meters, nape-breech measurement. At this time the branching col- 
umn of cells is accompanied by an artery that enters with the duct 
at the simple hilus and lies close to the developing basement membranes. ~ 
Capillaries forming an irregular plexus can be seen here and there 
about the ramifications of the simple tube forming the ductus sub- 
maxillaris. The arterioles, venules and capillaries at this stage are 
usually separated from the reticulated basement membranes by a short 
intervening mass of syncytium, but as the ducts increase in size this dis- 
tance is diminished. These relations can be found in stained sections 
from the glands of pigs 4$ to 6 centimeters in length. When, how- 
ever, the pig reaches an age represented by 84 centimeters, the injection 
of the gland becomes a simple matter and the description can be taken 
up from injected organs that are cut in half and studied under the 
stereoscopic microscope. This gives not only the relations of the ves- 
sels throughout their course, but also enables the observer to follow 
them in three dimensions. At this time the gland is reniform, and the 
vascular supply is comparatively rich. Since the relationship between 
arteries, veins and ducts established in pigs of earlier age always per- 
sists, the course of the ducts accordingly may be determined by the 
course of the blood-vessels. Indeed, in a pig of this age the duct and 
its branches are represented negatively, making it possible to follow 
them nearly as well as though they were either stained or injected. At 
this period the artery enters the primitive organ at the hilus and 
branches with the duct. This is the simple stage of the arteria submax- 
illaris. In its course the artery gives off small branches which almost 
immediately break up into capillaries. These run around the column 
of cells and empty at once into the vein accompanying the affer- 
ent vessel. The meshwork formed by this capillary plexus is small 
* Chievitz, Arch. f. Anat. u. Phys. Anat. Abth., 1885. 
oe 
- ‘ 
ee a ee ee ee ee en ee eee oe ae 
ee ee 
