Anatomy of the Umbilical Cord. 419 



machine, and cut from it- a number of consecutive sections, examining at 

 intervals, by careful measurements, the two arteries. I have seen no 

 reason to agree with the conclusions of Simpson and Neugebauer. Even 

 if their position were established it could only refer to the contracted 

 condition of the vessels after death, and this would afford no accurate 

 clue to their relative sizes during life. But even if it did it woidd not 

 explain, as I shall try to show, the spiral growth of the cord. 



In the investigation of this subject my first endeavour was to ascertain 

 which of the three tubes in the cord had the greatest influence in main- 

 taining the spiral, either before the cord was separated from its con- 

 nexions or after. If, while the cord was still attached to both mother 

 and child, I passed a needle through the cord close to the child, so as 

 to isolate the vein, and then compressed it against the needle, I found 

 that the spiral was completely maintained. On the contrary, if I com- 

 pressed the arteries and cord together towards the placenta, the cord 

 emptied and became flaccid, losing its spiral appearance. This was the 

 case very markedly in the instance of a cord which is the most perfectly 

 spiral in my possession. On distention by injection it showed a com- 

 plete helix in the remarkably short distance of an inch and an eighth 

 with a perfect lumen through the helix of three sixteenths in diameter. 

 In this cord the arteries coiled together within the helix of the vein. In 

 no cord which I have injected, and in which the twist was evident at all, 

 has it not been as evident that the vein was the main factor in the twist. 

 I have established this by distending, in a well-twisted cord, the three 

 vessels alternately with water. Distention of the vein induces the com- 

 plete spiral of the cord. Distention of one artery has little or no effect, 

 and distention of both arteries in no case equalled the results obtained 

 by distending the vein. I have injected both arteries with some slightly 

 resisting material, as stiff size, and after it has set I have distended the 

 vein with plaster of Paris, and in every case it has become evident that 

 the chief spirality lies in the vein. Injection of an artery with plaster 

 of Paris and allowing the whole cord to dry seldom produces a well- 

 marked spiral in any part of the cord, and never throughout its whole 

 length. A similar proceeding with the vein will produce a perfect spiral 

 throughout the whole length of any cord which has the twist running 

 through it. 



Neugebauer also found that blowing up the vein produced more marked 

 twisting of the cord than blowing up the arteries. In one of my specir 

 mens injection with plaster has done so over a length of three feet, and 

 the dried arteries are seen coiling round it; yet distention of these 

 arteries by water did not produce any spiral at all. In any regularly 

 spiral cord the arteries will always be found on injection to be within 

 the helix, a point which is very suggestive that the vein is the chief 

 factor in the production of the twist. In such cords as those in which 

 the whole development and the spiral are evidently deficient (and this 



