1876.] On the Anatomy of the Umbilical Cord, 417 



^Preliminary Note on the Anatomy of the Umbilical Cord"*. 

 By Lawson Tait, F.R.C.S. &c. Communicated by W. S. 

 Savory, E.R.S. Keceived April 28, 1875. 



[Plates 11, 12, 13, 14.] 

 I. Its external Form and Method of Growth. 



The peculiar twisted appearance of the human umbilical cord has re- 

 ceived much atteution from anatomists, aud 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 

 foetuses, 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 foetus of 

 certainly not more than thirteen weeks' development. 



Velpeau attributes the twisting simply to the rotation of the foetus. 

 Schroeder Yan der Kolk supposes that the blood flowing in the arteries 

 exerts a backstroke influence on the pelvis of the swimming foetus, 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 im- 

 pulse until very late in pregnancy. The revolution of the foetus 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 foetus 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 ex- 

 ternal dermal ring has been reached. Also I have seen the first revolu- 

 tion 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. 



Sir James Simpson (' Edinburgh Medical Journal,' July 1859) was of 

 * See Proceedings, vol. xxiii. p. 498. 



