372 GENERATION. 



to twelve pounds and twelve ounces avoirdupois. 1 As the 

 amniotic fluid accumulates and distends the amniotic mem- 

 brane, it becomes more and more closely applied to the 

 cord. This pressure extends from the placental attachment 

 of the cord toward the foetus, and gradually forces into 

 the abdomen of the foetus the loop of intestine, which, in 

 the early periods of intra-uterine life, forms an umbilical 

 hernia. 



It is generally stated by writers upon embryology that 

 the vessels of the cord present no valves ; but recent observa- 

 tions by Berger have demonstrated the presence of semi- 

 lunar folds, both in the vein and in the arteries. In the his- 

 torical account of this subject, given by Berger, it is stated 

 that many of the older writers described these folds more or 

 less accurately, and that they were observed more recently by 

 Hyrtl. Berger rejects the term valves, as applied to the semi- 

 lunar folds which he has observed, particularly as regards 

 those found in the umbilical vein. They are simple inversions 

 of the walls of the vessels ; and they do not exist in pairs, 

 nor do they seem to influence the current of blood. In the 

 arteries, these folds are situated at intervals of from half an 

 inch to two inches, and are more abundant where the vessels 

 are very contorted. In the vein, the folds are most abundant 

 near the placenta ; they are very irregularly placed, and, in 

 a length of four inches, fifteen folds were found. It is 

 not apparent that these folds have any physiological impor- 

 tance. 2 



As the allantois is developed, it presents, in the early 

 stages of its formation, three portions : an external portion, 

 which becomes the chorion, an internal portion, enclosed in 

 the body of the embryon, and an intermediate portion. The 

 intermediate portion, as we have seen, becomes the umbilical 

 cord. As the umbilicus of the foetus closes around the cord, 



1 LITTRE ET ROBIN, Dictionnaire de medecine, Paris, 1873, Article, Ombilical 



2 BERGER, Recherches sur la conformation interieure de la veine et des arteres 

 ombilicales. Archives de physiologic, Paris, 1871-1872, tome iv., p. 551, et seq. 



