234 Caroline McGill, 



The interstitial connective tissue of the adult smooth muscle is as 

 a rule ordinary areolar tissue. The connective tissue cells, at least in 

 some cases, appear to retain their primitive relation to the protoplasmic 

 syncytium (Fig. 22, ct). This is difficult to demonstrate, however, 

 because of the large number of collagenous flbrillae present and because 

 the granular protoplasm is much reduced in amount. The collagenous 

 fibers and elastic fibers are more numerous than in the foetal tissue 

 (Plate V, Figs. 24, cf and 27, el), though variable in amount in diffe- 

 rent places. The collagenous fibers may be arranged in a loose reti- 

 culum (Fig. 21), as a denser reticulum (Fig. 22), or where the muscle 

 cells lie very close together may be crowded into thin fenestrated 

 membranes (Plate XI, Figs. 25 and 26 cm). Such membranes have 

 been described by Watney (1876) and by Heidenhain (1900). 



The collagenous fibers, just as in development, are easily demon- 

 strated in material stained with Mallory's anilin-blue connective tissue 

 stain (Fig. 24). With this stain they appear extremely fine, but in 

 many places are united together into bundles. Here and there in the 

 adult they still apparently run through the protoplasm of the connec- 

 tive tissue cells or may be traced in among the myofibrillae of the 

 muscle cells (Fig. 24, at points marked mu). In Fig. 23 {ct) some of 

 the collagenous fibrillae are in connection at one end with the pro- 

 toplasm of smooth muscle and at the other with that of a connective 

 tissue cell. 



The elastic fibers are most easily demonstrated in material stained 

 with Weigert's elastic tissue stain [el, in Figs. 27 and 28), although 

 they also stain readily with iron-haematoxylin {el, in Figs. 21 to 23 

 and 25). They show the same general relations as in the later foetal 

 stages, running both longitudinally and circularly with respect to the 

 muscle fibers. It is only the longitudinally arranged elastic fibers that 

 are at times hard to differentiate from coarse myofibrillae as previ- 

 ously mentioned. The elastic fibers are rather coarse, homogeneous 

 structures, varying, however, greatly in thickness. They frequently 

 branch and anastomose with each other (Figs. 27 and 28, el). They lie 

 for the most part close beside the muscle fibers, some of them even 

 appearing to be embedded in the muscle protoplasm (Figs. 22, 23, 25 



