CHANGES IN FETAL VESSELS OF THE LIVER 509 



The fibrous connective tissue which had replaced or encroached 

 upon the vein varied from a poorly preserved dense fibrous 

 connective tissue to a very loose embryonic tissue which be- 

 cause of its gelatinous appearance suggested in the gross even, 

 the umbilical cord to a laboratory assistant (figs. 19, 20, 22). 

 It seldom contained any recognizable remnant of the lumen of 

 the original vein as stated by Kirchbach for the round ligament 

 of man. When the original lumen was preserved it had always 

 become much reduced and often multiple, as a result of folding, 

 as described by Baumgarten in man. In some cases the tissue 

 surrounding the remnant of the vessel was very loose and vas- 

 cular and the irregular outlines of the periphery of the wall of 

 the degenerating veins generally suggested that it was enclosing 

 the vein rather than that newly-formed elements of intimal origin 

 were actively transforming the vessel from within. Moreo\er, 

 the inner portion of the media was often better preserved and the 

 lumen of the vessel often contained some erythrocytes while the 

 outer portions of the media, on the contrary, were degenerated. 

 However had this process of degeneration been observed at 

 closer intervals in stages of a few days, e.g., it is not at all un- 

 likely that a certain amount of cellular infiltration, as described 

 by Baumgarten andHaberda in the neighborhood of the umbilicus 

 in man, might have been noticed in cats as well. 



The most striking thing about the microscopical structure of 

 the umbilical vein in the new born lamb is the variability in the 

 amount and distribution of the longitudinal nmscle fibers of 

 the media. In its extra-abdominal or cordal portion the struc- 

 ture of the vein was often found practically identical with that 

 of the distal extremities of the retracted arteries. The lumen 

 of the contracted vessel may be more or less stellate, crescentic, 

 or a mere slit not infrequently shaped like the printed capital I. 

 There is a single-layered endothelium. An elastica interna was 

 observed several times in sections stained with Van Gieson and 

 with orcein and fuchsin. The media contains longitudinally 

 disposed muscle fibers which are somewhat irregularly distrib- 

 uted, and between which elastic tissue is found. However, none 



