528 Caroline McGill. 



Heidenhain, Henneberg and Heiderich in the muscle of blood- 

 vessels. It is not the only type of contraction described for blood- 

 vessels. Heiderich, 1902, in the umbilical vessels found peristaltic 

 contraction. 



In the material studied in this investigation typical total contrac- 

 tion was not observed. In the smooth muscle of the blood-vessels of 

 dog, cat, pig, ox and man and in the sphincter pylori of Necturus 

 and dog, the contraction approaches the total type, Figs. 33, 34. The 

 contraction often involves all but the tips of the fibers, Fig. 33. 

 Here, as in determining the form of arterial muscle, the interpreta- 

 iton of sections is difficult. A fiber contracted in the middle, as in 

 Fig. 33 and Fig. 34 a, if cut through slightly obliquely or tangenti- 

 ally, would appear in section as a short, completely contracted fiber. 

 Fig. 34 b. In rare instances the contraction may involve the entire 

 fiber. More frequently the contraction passes over the fiber in broad 

 nodes involving from one-half to two-thirds of the fiber, Fig. 34, text 

 Fig. 5. Such fibers are well difl:"erentiated in material stained in Mal- 

 lory's anilin-blue connective tissue stain. The contraction node stains 

 orange, the uncontracted portion of the fiber red. It seems highly 

 probable that arterial contraction is only a modified contraction where 

 the contraction nodes are much longer and involve more of the fiber 

 than is usual in the peristaltic contraction in the muscle of the ali- 

 mentary canal or the urino-genital tract. In some places in the 

 carotid of the ox two or even more contraction nodes are present in 

 a single muscle fiber, thus producing a typical partial contraction, 

 Fig. 5, text Fig. 6. The contraction nodes in the muscle fibers of 

 blood-vessels are not as deeply staining as are those in the muscle 

 of the digestive and urino-genital tracts. Consequently the fibrillse 

 in material stained in either iron-hsematoxylin or Mallory's anilin- 

 blue connective tissue stain can in almost every instance be traced 

 through the contraction nodes, en in Figs. 33, 34. Fig. 34 shows them 

 in cross section of a contraction node. The cut ends of the fibrillse 

 show as fine dots. It is only when overstained that the contraction 

 nodes appear homogeneous as described by Henneberg and Heiderich. 



