514 ARTHUR WILLIAM MEYER 



of the lumen was produced by a projection into it of thick welts 

 or ridges or discontinuous longitudinal folds which however did 

 not concern only the longitudinal fibers of the media although 

 the contraction of these fibers, would, of course, result in an 

 increase in their caliber in a direction at right angles to the lumen 

 and hence would form folds which would have to encroach upon 

 it or produce a dilatation of the vessel. The latter was, however, 

 prevented by the active contraction of the circularis which 

 tended to reduce the size of the lumen or even to obliterate it 

 entirely and hence compress the longitudinal fibers. Since 

 the latter need more room folding of the wall would hence seem 

 to be the natural and inevitable result. It is interesting that 

 Strawinski, von Hoffman and Herzog have described similar 

 ridges in the unretracted hypogastric arteries in man. Haupt- 

 mann also found similar ridges in the noncontracted artery of 

 the horse and states that they "may be as prominent as those 

 described by Strawinski in man." Attention must be called 

 to the fact, however, that there are apparently two kinds of ridges 

 for Hauptmann attributed those found in the horse to large 

 irregularly arranged, branched intimal cells 200 to 300/x in size, 

 which are surrounded by dense fibrous tissue and lie directly 

 under the endothelium. Bucura, on the contrary, concluded 

 that the longitudinal ridges are due to contraction of the longi- 

 tudinal muscle fibers, while Pollot asserted that the ridges and 

 folds which project into the lumen of the ductus arteriosis are 

 undoubtedly not produced by a contraction but are an expression 

 of the unequal development of the constituents of the walls of 

 the vessels. Moreover, Pollot supports this opinion bj' results 

 obtained from experiments on the aorta of guinea pigs. These 

 consisted of the treatment of excised portions of the aorta with 

 adrenalin, a procedure which failed to i)roduce the ridges. 

 But since the retracted and contracted hypogastric arteries and 

 the umbilical veins in whose walls few longitudinal fibers were 

 present also contain welts or ridges, and moreo\'er, since thej" 

 are absent in the non-contracted vessels or portions containing 

 a large clot it is evident that they can be due to a contraction 



