Joseph Marshall Flint — 443 
penetrate the membrane limitantes and then join the plexus in the cap- 
sule. These arteries are accompanied by a single vein. Similarly, 
arteries are derived from the intralobular system which perforate the 
limiting membrane of the lobule and break up in the septum. Occa- 
sionally septal arteries will pass out through the primary or secondary 
septa and communicate with the capsular plexus. With the single ex- 
ception of this connection between the vessels of the framework and the 
glandular system, the circulation within the lobules is absolutely inde- 
pendent. The capillaries of adjacent lobules do not anastomose. Lim- 
iting membranes are not bridged by blood-vessels. 
2. The réle played by the circulation about the ducts in the secretion 
of the submaxillary is uncertain. Obviously they nourish the duct epi- 
thelium and therefore any part that the latter takes in the production of 
saliva must be traceable to this portion of the vascular system. 
3. The vascular system of the submaxillary develops pari passu with 
the ducts. The latter form the stimulus for the production of new 
blood-vessels. In the earliest stages the simple branching column of 
cells forming the submaxillary receives an arteriole which breaks up 
into a capillary plexus about the columns and finally empties into the 
vein accompanying it. The terminal buds of the cell columns are 
embraced by an irregular capillary plexus, the prototype of the future 
alveolar plexus. The circulation around each separate division of the 
main duct is independent, anastomoses between them occurring with 
great rarity. As the ramification of the ducts proceeds, they are fol- 
lowed by an extension of this simple vascular system. Venae comites 
are formed that accompany the main arteries from the sublobular inter- 
spaces to the hilus, and the simple capillary plexus about the main ducts 
develops into an irregular arterial, capillary and venous plexus. Finally, 
in a pig 18 or 19 centimeters long, the division of the ducts has increased 
to those of the lobular order and, as a result, a lobular circulation of 
simple type is finally produced. From this point the further develop- 
ment of the circulation is simply one of degree as the general plan is 
now completely established. A little later branches of the intralobular 
arteries perforate the limiting membrane and join the circulation devel- 
oping in the capsule and the septa. 
4. Like the blood-vessels of the adrenal, those of the submaxillary 
gland mark out the paths of development taken by the cell groups of the 
organ, forming, in a measure, a record of the ontogeny of its parts. 
This is known to be generally true of the systemic circulation and now 
holds for the submaxillary as well as the adrenal gland. It may then be 
