of Single Hypogastric artery in the Hainan Foetus. 337 
Finally, it may be repeated that fusion of bilaterally symmetrical 
vessels has occurred (cf. [c] supra). 
Evidently this type of single umbilical artery is very different 
from that found in specimen A. If attention is now turned again 
for a moment to specimen E, it will be seen that the latter in 
this respect resembles specimen F rather than specimen A. The 
chief difference between specimens E and F may be explained by 
the reflexion that in E the malformation is less symmetrical than 
in F„ 
General review and Summary. 
Two distinct types of the single umbilical artery are described 
in the foregoing paragraphs. In the first instance, one of the two 
normal hypogastric arteries has failed to develop, or has been 
completely suppressed, while the other one has become enlarged. 
In the second type an entirely different history obtains, and 
the abdominal arterial system contains an abnormal vessel into 
the formation of which two elements have entered, viz. a seg- 
mental splanchnic artery, and the primitive ventral aorta. From 
this compound vessel the single umbilical artery is derived. 
In examples of the first kind the dorsal abdominal aorta remains 
unaffected, whereas in those of the second variety the dorsal 
aorta is of insignificant size. The effects upon the common iliac 
arteries are also different in the two cases. After drawing up this 
account and the conclusions based upon it, I found that Professor 
Weigert (in Virchow’s Archiv, Band 104, p. 10), had already recog- 
nised a distinction between two classes of this anomaly. The 
reference to Professor Weigert’s work I owe to the bibliography 
appended to a very admirable paper by Dr J. W. Ballantyne (in 
the Edinburgh Obstetrical Transactions, Vol. 23, 1897 — 98, p. 54). 
Any claim to originality in the present communication must 
therefore be based upon the more detailed explanation of the 
connexions of the several arteries concerned. I wish to record my 
indebtedness to Professor A. Robinson for useful hints in respect 
of this part of the work. 
Professor Weigert’s paper contains descriptions of three 
specimens. Of these, No. i. appears to have resembled closely my 
specimen A in respect of the arrangement of the abdominal 
arteries. Professor Weigert’s second specimen agrees closely with 
my specimen F, though it is not clear to me whether No. ii. was 
symelian or not. Finally, Professor Weigert’s specimen No. iii. 
must have been almost identical with my specimen E. 
