Anatomy of the Umbilical Cord. 439 



is probably only an early stage of the more perfect plan already de- 

 scribed, for I have only found it in this one case. 



The foetus in which the observation was made was a large one, but 

 not fully developed, having probably not reached within six weeks of 

 maturity. The injection was very successful, and was made under a pres- 

 sure of only 100 millims., and the plexus of vessels was seen to extend 

 about 5 millims. over the venous surface of the cord (Plate 13. fig. 21, b). 

 But on examining the vessels with a power of thirty diameters, it is readily 

 seen that these capillaries did not return in loops, but seemed to be lost 

 in the substance of the cord — contrasting in this relation very markedly 

 with the capillaries of the dermal riug, from a large trunk of which 

 they arose. These latter are arranged in loops for the return of the 

 circulation, as is the case with capillaries almost everywhere else; but 

 those in the cord have an arraugement more like that of the branches 

 of a tree. Further, it is noticeable that the capillaries spreading over 

 the surface of the cord may be seen to arise by the aggregation of 

 smaller roots, just as I have pointed out to be the case in the forma- 

 tion of the central sinus of the cord (Plate 13. fig. 21, a). 



None of the canalicular tissue of the cord could be seen to have been 

 injected from these capillaries ; but the pressure used was too low to 

 accomplish that, as the injection had to be made for another purpose. 



The umbilical cord in this case had been cut off about 60 millims. 

 from the dermal ring, and the injection as usual was made from the 

 vein. 



On making a section of the cord immediately below the ligature which 

 retained the injecting nozzle, a small spot of injection was seen in the 

 substance of the cord lying close outside the wall of the vein. This was 

 found to be the central sinus of the cord ; and on being carefully traced 

 towards the foetus, it was found to curve spirally close alongside the vein 

 and to enter and pass through the omphalic canal in the midst of the 

 three vessels. 



Throughout its course, examination by a power of thirty diameters 

 showed that it gave off branches which rapidly broke up and were lost 

 in the tissue of the cord. 



Finally, it was found to arise from several small branches, four of which 

 at least are preserved and are represented in the drawing (Plate 13. fig. 19). 

 They arose from the lower intercostal arteries, and gathering together on 

 the lower surface of the omphalic vein, combined in the omphalic canal 

 to form the sinus. 



From this case it is evident that this sinus at least occasionally passes 

 very far into the cord, as the point where it was discovered was at 

 least 45 millims. from the dermal ring. 



(I think it is possible that the radicles of this sinus may be what 

 Kolliker described as the nerve-twigs derived from the hepatic plexus.) 



