UMBILICAL PHLEBITIS OF NEW-BORN ANIMALS. 401 



The first is formed of t\YO arteries and two veins, in contra-dis- 

 tinctiou to tire condition in soli})eds, where the cord only contains one 

 vein. In the second, the arrangement is as follows: The two umbilical 

 allantoid arteries on entering the abdomen curve backwards towards the 

 entr}' of -the pelvis, passing over the sides of the bladder enveloped in 

 the lateral ligaments, and extend upwards towards the bifurcation of the 

 aorta, finallj' pouring their contents into the internal iliac arteries. In 

 the adult they niay still be traced as annexes of these latter vessels. 

 The two umbilical veins on passing through the ring unite to form one 

 within the abdomen. This vessel passes forwards, rising along the 

 lower abdominal wall, then becomes lodged in the thickness of the 

 inferior middle ligament of the liver, and finally penetrates that organ 

 where it unites with the portal vein. It is also connected with a vessel 

 known as " the vein of Arantius," which places it in communication with 

 the posterior vena cava, a vein not found in solipeds. 



The foetal blood is purified by exchanges between it and that circu- 

 lating in the maternal placenta, and when re-arterialised it returns by 

 the umbilical vein. 



The urachus, found in the embryo and fcetus, eventually gives rise 

 to the bladder. In new-born animals this viscus is therefore open at 

 its .base, and communicates with the allantoid cavity through the 

 urachus. The urachus starts from the base of the bladder, and, extend- 

 in" along the mediair plane of the lower abdominal wall between the two 

 umbilical arteries as far as the umbilical opening, takes its place in the 

 cord alongside the vessels. Through it the secretions of the foetal 

 kidneys drain into the allantoid cavity. The interstitial mucous tissue, 

 also called " AVharton's jelly," is a gelatinous material which unites 

 these different vessels and helps to support and protect them in the 

 umbilical cord. It is particularly abundant opposite the umbilicus. 



Immediately after birth the umbilical cord ruptures of itself as a 

 result of the fall which the young animal experiences or of movements 

 made by the mother, as for instance when she attempts to rise. In 

 certain other cases it is divided by the mother biting it, or it may be 

 ligatured by some person present. However the rupture may be 

 brout^ht about, it always occurs at a distance of 2 to 4 inches from the 

 umbilicus. The immediate result is to produce thrombosis of the 

 umbilical vessels and obstruction of the urachus. The two umbilical 

 arteries rarely bleed, for haBmostasis is brought about by stretching, 

 and these arteries, being very elastic, almost immediately retract and 

 close. The umbilical veins simultaneously become blocked, and the 

 sino-le intra-abdominal vein having no further raison d'etre, gradually 

 becomes obliterated. The urachus should normally be obliterated at 

 the moment of delivery (Colin and Saint-Cyr), or at any rate soon 



D.C. D D 



