Joseph Marshall Flint — 427 
submaxillaris in the adult. It is very easy, moreover, to follow in a 
single, well-injected gland the evolution of the duct circulation from 
that of the lobular type to that which embraces the main duct. The 
small arterioles break up into capillaries and reunite into small venules 
that finally terminate in the accompanying veins. ‘These vascular ele- 
ments enlarge so that the arteries branch and come to lie upon the capil- 
lary plexus and the isolated veins 
receive a few anastomoses from 
each other. With the growth of the 
duct and the lengthening of the 
artery and its ramifications, the 
venules which are last formed from Fia.4. Circulation about an intralobular 
eapillacics: conte to ler undernthe Gg, phe artery isthe upper vessel of the 
arterial but over the capillary sys- 
tem, and thus we have the three superimposed series of vessels noted about 
the ducts of the larger order. Throughout the course of the successive 
divisions of the submaxillary arteries, branches are given off which supply 
the framework of the interspace. These vessels are extremely irregular 
and after breaking up into a capillary system that ramifies around the 
fascicles of connective tissue, venules are formed emptying into the venae 
comites at irregular intervals. The circulation to the sympathetic gang- 
lia buried in the interspaces also has a similar derivation. 
CIRCULATION OF THE CAPSULE AND SEPTA. 
Blood-vessels that run to the primary and secondary septa are derived 
from the Aa. intralobulares. Branches from vessels of the latter type 
perforate the limiting membrane and almost immediately break up into 
a loose irregular plexus, the venules from which unite into a single vein 
that accompanies the septal artery and flows back into the lobular circu- 
lation. The blood-vessels in the capsule are derived from two sources, 
in part from the arteries and veins in the periglandular connective tissue 
which run on the surface of the connective tissue envelope of the organ 
in the form of a very irregular plexus of polygonal spaces. These vessels 
are very small. Frequently capsular branches from the lobular arteries 
perforate the capsule and join the capsular plexus. These capsular 
arteries are accompanied by capsular veins. When septal arteries arise 
from lobules at a point near the capsule, they may pass from the septa 
and finally unite with the capsular plexus. With these two exceptions, 
the circulation in each lobule seems to be complete and independent, 
save in those cases where a lobule of the first order is not completely 
