THE CORD.
The umbilical cord is the organ through which the foetus communicates with the mother. Until after the allantoic vesicle is formed and the um bilical vessels develop, the cord does not exist. It then forms a conduit folded in the amniotic sheath, and contains in its interior the pedicle of the umbilical vesicle and the pedicle of the allantois. The former pedi cle atrophies and becomes filamentous, and the cord itself is formed by the pedicle of the allantois containing the umbilical vesicles and by its amni otic sheath. At first short and thick, the cord becomes gradually thinner and thinner as the abdominal walls and the cutaneous umbilicus are formed. A loop of intestine penetrates a certain distance up the cord, and sometimes ascends so high at the time of the closure of the umbilicus as to constitute congenital umbilical hernia.
As it becomes longer the cord loses its swollen appearance, and it be gins to assume a spiral shape at the beginning of the third month. At term the trunk is about as thick as a finger, and is white and polished in appearance. It is more or less transparent and shows the tortuous bluish trace of the umbilical vein.
I. Length of the Cord.-18 to 24 inches is the average length; but it is common to find cords longer or shorter than this. The shortest we have seen measured 11.2 inches, the longest 52 inches. Tarnier, in his re searches at la Maternit(, found one of 6.8 inches, and one of 46.4 inches. Churchill had one 88 inches long, Schneider one 120 inches long. The length of the cord is not without importance for the foetus, for it is ex posed to compression, displacements and entanglements which may more or less compromise the infant's existence.
Volume of the Cord.—The cord may be fat or lean, as more or less of the gelatine of Wharton is present.
ILL the great majority of cases the cord is twisted upon itself from left to right. (Figs. 140 and 141.) Tarnier, in 550 cords found twisted to the left 505; to the right 45. Nengebauer, in 150 cords found twisted to the left 114; to the right 39. Hecker, in 315 cords found twisted to the left 245; to the right 70.
The cause of this torsion has been variously attributed to the gyratory movements of the embryo, to the fact that the vessels develop more rap idly than the sheath, etc. We do not know the cause with certainty.
The number of spirals varies greatly: Thus, Kilian has seen 12 to 17, Blume 33, Dohrn 55, and Meckel 95. In these cases Wharton's jelly may be entirely absent at the twisted points, and the life of the infant may be endangered from embarrassment of the qirculation. Complete atresia
and death of the katus may follow (cases of Meckel, Dohrn, Blume, Kilian, d'Outrepont, Elsiisser, etc. (Figs. 142 to 147.) In some twin births the cords are united or laced together. Chantreuil has collected a number of these cases.
We often find nodosities due to excess of gelatin and angles formed by wasting of the vessels. (See Figs. 140 and 141.) IV. cord stretches from the cutaneous umbilicus to the placenta. A prolongation of skin from the umbilicus encircles it for a short distance.
The skin ceases abruptly at the level of its continuity with the cord, and at this point there is a capillary circle that embraces the base of the cord, and extends up it for several lines. This vascular circle is in con nection with the artery and vein of the abdominal skin at each side of the median line of the body. The epidermis of the body above is continu ous with the epidermis of the cord. These capillaries, after running some 2-3 lines to the edge of the skin, return and pour their blood into the circular vein.
This disposition of the skin and its vessels explains the fact that the cord always atrophies to the level of the skin, no matter where the cord is tied.
The placental insertion of the cord is not absolutely fixed. When situ ated at or near the centre of that organ, it is termed central; when placed near the edge, it is called marginal. (Fig. 149.) In the latter case there is always a dissociation of vessels that border on different points of the placental circumference. In a few cases, less rare perhaps than is gener ally supposed, for we have ourselves seen three instances, the cord does not go to the edge of the placenta, but penetrates the membranes, and accompanies them for a longer or shorter distance. This is the velamen tons insertion (Fig. 150); and beyond this point the vessels reach the edge of the placenta, travelling either together or alone in a forked man ner so as to form the forked insertion. (Fig. 148.) Finally, Chantreuil has mentioned exceptional cases in which the cord adheres to the body of the embryo, or to the amnion, or when the branches adhere to one another. They coexist almost always with placental ad hesions, or with foetal monstrosities. Further, the anomalies and lesions of the umbilical vessels, and the tumors of the cord which are associated with the hydatid mole, are to be mentioned.