Anatomy of the Umbilical Cord. 431 



It is then quite easy to discriminate between the canalicular and 

 muscular tissue ; but in the unprepared, or in the stained section, it is 

 impossible to decide where exactly the muscular fibre begins, especially 

 if the blood-vessel has been distended, for then the layers of canalicular 

 tissue immediately outside the blood-vessel are stretched so as to be 

 parallel in direction to the general course of the muscular fibres. It 

 will be seen, therefore, that the whole column of the cord constitutes the 

 external coat of the blood-vessel, and also the substitute for the vasa 

 vasorum which are seen in other arteries. 



I have already described an arrangement of blood-vessels at the root 

 of the cord when speaking of its method of growth, but something more 

 must here be said on this point. When the nozzle of the syringe is tied 

 into the still attached cord an inch or two from the foetal insertion, with 

 the stream towards the foetus, the injection is made to travel with some 

 difficulty, and it is always found to terminate in a sort of cone outside 

 the blood-vessel, the apex of which is just within the dermal ring (Plate 12; 

 fig. 13). At this point it seems impossible to get the injection to travel 

 round the blood-vessel as it does elsewhere in the cord — that is, I have 

 failed to get it to enter the subcutaneous tissue on the other side of the 

 omphalic ring ; and, as will be seen in the same specimen, I have been 

 equally unable to get it to travel from the subcutaneous tissue into the 

 substance of the cord even under so great a pressure as 500 millims. 



"When the extreme apex of the cone obtained by injecting the substance 

 of the cord near the ring is examined by sufficient power, it will be seen 

 that the injected canals (Plate 12. fig. 14) run up to and border immediately 

 upon the nucleated fibrous and muscular tissue which constitutes the 

 omphalic ring. I have failed to inject any capillaries from the tissue in 

 this way. 



It is clear, then, that there must be some special arrangement for the 

 nutritive supply of the substance of the cord, as it does not obtain any 

 assistance from the umbilical vessels ; and mere stomatic absorption, 

 though I think it undoubtedly plays a most important part in the 

 nutrition of the cord, could hardly be considered as sufficient to do the 

 whole work. 



"When the capillary plexus running from the dermal ring (already 

 described) has been successfully injected, I have found that a peculiar 

 vascular arrangement is also displayed in the centre of the cord, lying in 

 the firm nucleated tissue which forms the omphalic ring, and to which is 

 due unquestionably not only the process of growth of the cord, but also 

 in great measure its nutrition and the processes of closure of the vessels 

 of the ring, and the removal of the stump by inflammatory ulceration. 



The basis of this arrangement is a peculiar sacculated sinus, a mere 

 excavation in the fibrous tissue, as I have been quite unable to demon- 

 strate any definite wall for it. It seems to have a spiral arrangement ; 

 for in section (Plate 13. fig. 15) it appears and disappears as only a screw 



