No. 3-] UTERUS AND EMBRYO. II 
3 4 
the surface of the chorion, marking their course by projecting 
ridges. The insertion of the cord is always, so far as I have 
observed, obviously eccentric ; the degree of eccentricity varies 
from a nearly central position to the so-called velamentous in- 
sertion,—compare B. S. Schultze, 159; the degree of eccen- 
tricity is easily seen to be related to the distribution of the 
vessels, —a point not mentioned in current text-books. The 
arteries come down together from the cord, and are usually 
connected, but not invariably, by a short transverse vessel, 
situated about half an inch above the surface of the placenta, 
and which has been noted by many observers. I have never 
noticed any arterial or venous anastomoses on the surface of the 
placenta. The two kinds of vessels do not run together; the 
arteries lie nearer the surface, the veins deeper, Cut 26; 
the arteries fork separately until they are represented only by 
small branches and fine vessels; some of the small branches 
disappear by dipping down suddenly into the villi below; the 
veins are considerably larger than the arteries, and some of the 
larger branches disappear from the surface in the same abrupt 
manner as do the smaller arteries. There is the greatest possi- 
ble variability in the vessels of the placenta; I have never seen 
two placentz with the vessels alike. The more eccentric the 
insertion of the cord, the more do the vessels tend to distribute 
themselves symmetrically ; the more central the position of the 
cord, the less can any vascular symmetry be made out. 
The two following paragraphs are copied without change 
from my article on the placenta (Buck’s Reference Handbook of 
the Medical Sciences, V., 696, 697) : — 
“To follow the course of the foetal blood-vessels within the 
placenta, the best method is by corrosion injections. These 
may be made either with fusible metal, wax, or celloidine. The 
first is specially suited for the study of the large trunks; the 
latter, for that of the smaller vessels also. I have a very beauti- 
ful celloidine injection by Dr. S. J. Mixter, which, with others of 
wax and metals, has served as the basis of the following descrip- 
tion: The veins leave the surface somewhat more abruptly than 
do the arteries, which gives off more small branches to the sur- 
face than do the veins, Cut 26. Both kinds of vessels leave 
the surface by curving downward for a short distance into the 
trunk of a villus; the vessels then divide, and their branches 
