442 The Submaxillary Gland 
22 centimeters long it is not uncommon to meet with alveoli without 
mucous cells. These may be, in part, alveoli of the serous type which 
we find in the adult, but probably also represent a group in which 
mucous cells have not yet developed. 
RESUME. 
1. The blood-vessels of the submaxillary gland form practically three 
circulatory systems: 
(a) The glandular system in which the main artery enters the gland 
at the hilus rapidly approaches the ducts and runs with them in the 
interlobular spaces until the lobules are penetrated where the arteries 
terminate in a capillary plexus around the alveoli. From these capil- 
laries venules are formed which follow the course of the arteries, leave 
the lobule at the hilus where they become duplicated into the venae 
comites of the main arteries. They now run with the arteries, giving 
off frequent anastomoses which pass over and under them, and finally 
leave the gland at the hilus to empty into the V. facialis communis. 
(b) A system around the ducts, the arteries of which are derived 
from the ramifications of the main arteries of the submaxillary gland, 
the branches of which course in the connective tissue about the ducts 
forming around those of the higher orders a simple indefinite arterial 
plexus. The ultimate terminals pass downward and divide into a 
capillary network just beneath the epithelium lining the ducts. Small 
veins originating from the union of capillaries pass upward and unite 
into larger venous elements to form an irregular plexus of veins just 
beneath the arteries. Larger emissary veins leave this plexus and flow 
as tributaries into the venae comites accompanying the main arteries. 
In the interlobular system both the arterial and venous plexuses become 
less definite, but the scheme of the duct circulation is the same. In 
ducts of the sublobular order there is no definite arterial or venous 
plexus, the capillary plexus still persists and the arteries and veins lie 
above it. The same thing is true of the lobular and intralobular ducts 
except that the circulation about them is much simpler. 
(c) The circulation in the framework. A well-marked capsular plexus 
is derived from vessels in the periglandular connective tissue. These 
run on the surface of the submaxillary gland and break up into an irreg- 
ular arterial plexus formed of polygonal spaces. Venae comites accom- 
pany the arteries. Derivatives of this plexus give off the capillaries to 
supply the capsule which unite into venous radicals and flow into the 
accompanying veins. Occasional branches from the intralobular arteries 
