Umbilical Cord
or NAVEL STRING, the bond of communication between the fœtus (which enters at the um bilicus, or naval) and the placenta, which is attached to the inner surface of the maternal womb. It consists of the umbilical vein lying in the center of the two umbilical arteries winding from left UMBRELLA BIRD to right round the vein. Contrary to the usual course, the veins convey arterial blood to the fœtus, and the arteries return venous blood to the placenta. These vessels are embodied in a yellow gelatinous matter, known from its first descrimatter ber (in 1659) as Wharton's gelatine.
Nervous filaments have been traced into the cord; but the presence of lymphatics is doubtful. The whole is invested by a membrane (the amnion), and its ordinary length is about 20 inches. As soon as a child is born, and its respiration fairly established, the umbilical cord is tied, and divided near the navel, which spontaneously closes, the fragment of cord dying away.