Joseph Marshall Flint | 429 
and irregular and the vessels composing it are often unequal in 
caliber. Following the branching ducts, the A. submaxillaris divides 
with each successive ramification, giving 
off still the collateral arterioles that em- 
brace the walls of the ducts. The rami- 
fication at this time extends to about four 
orders and the arterioles terminate in a 
capillary plexus embracing the terminal 
buds or swellings that form the apices of 
the growing ducts. These vary in num- 
ber from four to seven and are distinctly 
seen as clear spaces sharply demarcated by 
the embracing capillary plexus. At this 4,45 submaxillary land of pig's 
ace ine terminal capillary esystem= sur embryo Sicentimevers lone, injceued 
with silver nitrate and cut in half. 
> 4 2 ei Fa SLE , X% 10 diameters. The simple arteri- 
rounding each group of primitive alveoli 3).) and oacillary ploxus around che 
are entirely independent and have as yet Srowing column ot cellsis distinctly 
WO SAAS LOMORes: Ayihl cacherothere “ihe Svensk tho\erminal pads anaye Re 
blood, derived from the terminal arteri- 
oles, passes through the capillary plexus and is gathered again into 
venules which accompany the terminal artery along the walls of the duct 
from which the buds have grown, but the alveolar plexus is finer than 
that around the ducts. Already at this stage, it is possible to see that the 
blood supply of the entire gland now looks like the vascular distribution 
in a single lobule of the adult organ. Attention has already been called 
to the analogy between the two, so the four ramifications of the A. sub- 
maxillaris; Aa. principales, Aa. interlobulares, Aa. sublobulares, Aa. lob- 
ulares are like the divisions of the intralobular arteries in the adult. 
Fig. 5 represents half of an injected gland at this stage, photographed 
so as to obtain a stereoscopic effect. The branching of the ducts is shown 
by the course of the blood-vessels and the irregular plexus formed by the 
latter upon the former is clearly visible. The alveolar plexus, however, 
does not stand out clearly in this specimen. ; 
In a pig 12 centimeters in length the ramification has proceeded to 
higher orders, the ducts as shown by the embracing meshwork have 
increased in size and the plexus embracing them is more highly differ- 
entiated. Small lateral arterioles are now given off from the main 
arteries which divide into capillaries. These reunite into little venules 
emptying into the main venae comites. In a pig 8 centimeters in length, 
the veins are duplicated as high as the third order, but have not yet taken 
up their course in such close relation to the artery. In the next stage, 
however, the veins follow more closely the course of the artery and the 
