UMBILICAL CORD. 809 



coming from the body of the foetus, which are twisted usually from left to 

 right, around the single umbilical vein. In addition to the spiral turns of 

 the arteries around the vein, the entire cord may be more or less twisted, 

 probably from the movements of the foetus. 



The fully developed cord extends from the umbilicus of the foetus to the 

 central portion of the placenta, in which its insertion usually is oblique ; 

 although it may be inserted at other points, and even outside of the border of 

 the placenta, its vessels penetrating this organ from the side. Its usual 

 length, which varies very considerably, is about twenty inches (50 - 8 centi- 

 metres). It has been observed as long as sixty (152'4 centimetres), and as 

 short as seven inches (17*8 centimetres). When the cord is very long, it 

 sometimes presents knots, or it may be wound around the neck, the body or 

 any of the members of the foetus ; and this can be accounted for only by the 

 movements of the foetus in utero. 



The external covering of the cord is a process of the amnion ; and as it 

 extends over the vessels, it includes a gelatinous substance (the gelatine of 

 Wharton) which surrounds the vessels and protects them from compression. 

 This gelatinous substance is identical with the so-called membrana inter- 

 media, or the substance included between the amnion and the chorion. The 

 entire cord, covered with the gelatine of Wharton and the amnion, usually is 

 about the size of the little finger. According to Eobin, the umbilical cord 

 will sustain a weight of about twelve pounds (5 - 4 kilos). As the amniotic 

 fluid accumulates and distends the amniotic membrane, this membrane be- 

 comes more and more closely applied to the cord. The pressure extends 

 from the placental attachment of the cord toward the foetus, and it gradu- 

 ally forces into the abdomen of the foetus the loop of intestine, which, in the 

 early periods of intrauterine life, forms an umbilical hernia. 



The vessels of the cord, the arteries as well as the vein, are provided 

 with valves. These 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 half an inch to two 

 inches (12-7 to 58'8 mm.), and they 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 (10 centi- 

 metres), fifteen folds were found (Berger). It is not apparent that these 

 valvular folds have any physiological importance. 



As the allantois is developed, it presents, in the early stages of its forma- 

 tions, 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 becomes the umbilical cord. As the 

 umbilicus of the foetus closes around the cord, it shuts off a portion of the 

 allantois, contained in the abdominal cavity, which becomes the urinary blad- 

 der ; but there is a temporary communication between the internal portion 

 and the lower portion of the cord, called the urachus. This generally is 

 obliterated before birth and is reduced to the condition of an impervious 

 cord ; but it may persist during intrauterine life, in the form of a narrow 



