Preliminary note on the anatomy of the umbilical cord

Abstract

The peculiar twisted appearance of the human umbilical cord has received much attention from anatomists, and has been the subject of much ingenious speculation. According to Velpeau (‘ Embryologie’) the torsion begins as early as the seventh or eighth week, whilst Burdach has not observed it earlier than the tenth. I have repeatedly seen fœtuses, apparently of the twelfth and thirteenth week, in which no appearance of twisting was observable in the cord, though one of the most perfectly twisted cords in my possession belongs to a fœtus of certainly not more than thirteen weeks’ development. Velpeau attributes the twisting simply to the rotation of the fœtus. Schroeder Van der Kolk supposes that the blood flowing in the arteries exerts a backstroke influence on the pelvis of the swimming fœtus, thus determining its revolution in one direction or the other, as the arteries are to be found to the right or left of the vein. In order to dismiss this view we have only to recollect that the umbilicus could not in any way become a fixed axis, and that the mechanical arrangement of the heart, in the non-separation of its streams, would yield but a very weak impulse until very late in pregnancy. The revolution of the fœtus is not known to occur, though its occurrence is probable. Such revolution occurs in the spawn of the frog as early as the first segmentation of the black sphere; but then it is evidently the result of the necessity there is for an equal exposure of all parts of the embryo to the action of light and heat, just as the germinal spot is always uppermost in the bird’s egg. No such necessity exists in the persistently included mammalian ovum, and the revolution of the fœtus cannot be accepted. If it did occur it is highly improbable that the revolutions could number only from four to eighteen, these being the ranges I have noticed in a large number of fully developed cords. Another objection to Schroeder’s hypothesis is that, as a matter of fact, the arteries leave the omphalic ring nearly always below the vein and symmetrically arranged in relation to it. Their passage to one or other side of it is seldom apparent till the external dermal ring has been reached. Also I have seen the first revolution of the arteries pass from right to left, after which they suddenly bent on themselves and passed up the cord in an irregularly straight course, whilst the vein maintained the normal spiral. Further, I have seen the arteries reverse their course about the middle of the cord, though the vein maintained the uniform spiral.