Joseph Marshall Flint 421 
1. The glandular circulation from the A. submaxillaris to the alveo- 
lar plexus and back to the Vy. submaxillaris. 
2. The circulation about the ducts. 
3. Circulation in the capsule and septa. 
THE GLANDULAR CIRCULATION. 
The submaxillary artery in pigs at the hilus or point of entrance is 
separated by a short distance from the ductus submaxillaris. The two 
rapidly converge, however, and, as a rule, meet just before the point 
where ducts of the primary order are found. Before joining the duct, 
the artery may give off one or two short branches that enter adjacent 
lobules, as well as a few branches to the large mass of connective tissue 
which enters the organ at the hilus. The ducts of the first order are 
accompanied by the Aa. principales. ‘These now run in the connective 
tissue of the larger interspaces at a short distance from the lumen of 
the duct. There is no marked tortuosity of the main artery or its prin- 
cipal branches, but, at the different angles where the chief ducts are 
given off, the arteries sometimes wind partly around them or may take 
a slightly spiral course about the duct. As a rule, however, while there 
is a slight wavy irregularity in the course of these vessels, a complete 
spiral arrangement about the ducts is rarely observed. From the prin- 
cipal branches of the main artery the Aa. interlobulares are derived, 
accompanying ducts of the same order in the interlobular interspaces. 
From these branches the blood is distributed in radiating directions 
throughout the gland. They are longer than blood-vessels of any other 
order. In their course they may divide once or twice and finally ex- » 
haust themselves in lateral branching in the sublobular arteries which 
run with the sublobular ducts in the center of the primitive lobules. 
Arteries of this order may in thick injected specimens be easily recog- 
nized running in the center of the groups of ultimate lobules bounded 
by the secondary septa. They divide three or four times with the sub- 
lobular ducts and then exhaust themselves in the Aa. lobulares, each 
one of which enters a primitive lobule at its hilus together with the 
lobular duct. Once within the limiting membrane of the lobule, the 
ramification is more abrupt and more marked. The intralobular branches 
of the A. lobularis radiate from the hilus toward the periphery of the 
lobule, divide with and accompany the intralobular ducts. The ter- 
minal divisions of the intralohular arteries run with the intercalary 
ducts and divide under the clusters of alveoli into the alveolar capillary 
plexus. The capillaries mount up over the alveoli external to the re- 
ticulated basement membrane and anastomose with the capillary plexus 
29a 
