364 MALL. [VoL. XIV. 
branches, one near the middle line and one more lateral. A 
more ventral group of segmental arteries supplies the Wolffian 
body. The blood from all these groups of arteries appears to 
be collected by the cardinal veins; certainly that from the 
ventral and lateral group is. 
The lateral group gives rise to the intercostal arteries by first 
supplying the myotomes, and, as these grow into the membrana 
reuniens by a process of budding, the vascular loop follows it. 
In so doing the loop is first on the dorsal side of the sympathetic 
and finally on its lateral side, thus making the sympathetic cord 
cross the intercostal arteries and veins on their ventral side, as 
is the case in the adult. 
No sooner is the vascular loop extended to the lateral side of 
the sympathetic than it begins to anastomose with neighboring 
segmental loops, as single vessels near the subclavian and hypo- 
gastric arteries, and as a plexus midway between these two. 
This gives us at this early period a complete anastomosis from 
the subclavian to the femoral artery, as Fig. 16 shows. It 
remains only for this system to shift around towards the median 
line with the muscle, nerves, and ribs to form the condition of 
things as found in the adult. 
Fig. 16 shows that the upper and lower segmental arteries 
of the series do not correspond with the same in the adult. 
Above the superior intercostal is missing, while below there is 
only a small fourth lumbar present, and it arises from the middle 
sacral. Ilio-lumbar and circumflex-iliac arteries are altogether 
wanting, and I should judge from the relation of the arteries in 
embryo XLIII that the arch formed by the ilio-lumbar and 
circumflex-iliac is of secondary origin and has nothing to do 
with the segmental arteries. That they form anastomoses with 
the lower lumbar arteries in the adult can be explained in other 
ways. 
The hypogastric artery is present long before the segmental 
arteries are formed near its junction with the aorta, and on that 
account we can no more call the trunk of the common iliac 
artery segmental than we can apply the same term to the 
descending aorta. We can only locate its origin in the 
neighborhood of the fourth lumbar artery. 
