294 SURGICAL APPLIED ANATOMY. [Chap. XVT. 



The fibrous ring of the umbilicus is derived from 

 the linea alba. To this ring the adjacent structures, 

 skin, fasciae, and peritoneum, are all closely adherent. 

 The adhesion is such, and the amount of tissue 

 between the skin and peritoneum is so scanty, that in 

 operating upon an umbilical hernia it is scarcely 

 possible to avoid opening the sac. 



In the foetus three vessels enter at the navel, and 

 immediately separate on reaching the abdominal cavity, 

 the vein passing directly upwards and the arteries 

 obliquely downwards. Running down from the um- 

 bilicus in the middle line is also the remains of the 

 urachus. In the foetus, the spot where the three 

 vessels part company is about the centre of the navel, 

 and it thus happens that in a congenital umbilical 

 hernia the gut as it escapes separates the three vessels, 

 which become to some extent spread over it. The 

 congenital hernia, indeed, works its way in among the 

 structures of the cord and receives its main coverings 

 from them. These hernise are fortunately rare, for in 

 certain instances they extend some way into the cord, 

 and in at least two reported cases the gut was cut across 

 by the accoucheur in dividing the cord at birth.* As 

 the abdomen increases in height the contraction of the 

 two obliterated arteries and of the urachus drags upon 

 the cicatrix and pulls it backwards and downwards. 

 Thus, in the adult umbilical ring, as viewed from the 

 inner side, the cords representing not only the obli- 

 terated arteries and the urachus, but also the vein, 

 appear to start from the lower border of the cicatrix. 

 In adult hernise, indeed, the gut escapes above both the 

 oblitei-ated arteries and the vein. The upper half of 

 the cicatrix is thin when compared to the lower half, 

 and is "supported also by less firm adhesions. 



* The congenital hernia must be distinguished from the infantile 

 umbilical hernia so commonly met with after separation of the 

 cord. For an account of these congenital hernias, see paper by the 

 author in the Lancet, vol. i., 1881, p. 323. 



