Fibroglia Fibrils m the [ntestinal Wall of Nectum 



these fibrils bear to the granular protoplasm surrounding the nucleus 



and the fact that they always slain as docs this protoplasm, is further 

 evidence for their being protoplasmic. 



Of course, the conclusive evidence as to the nature of the fibro- 

 glia fibrils can only be definitely obtained when their function is clearly 

 determined. That is whether they be contractile or not. Along this 

 line I have no direct evidence. However, in the intestine of Necturus 

 where these fibrils were studied, the muscular coat had in some in- 

 stances been contracted by stimulation, either electrically or otherwise 

 before fixation. In the subepithelial connective tissue of portions of 

 the intestine so contracted, the collagenous fibrils often run a distinctly 

 wavy course, yet the fibroglia fibrils always run a comparatively straight 

 course (Fig. 5). Were these fibrils non-contractile, in firmly contracted 

 material they would show decidedly wavy. Thus there is some evi- 

 dence for believing that these fibrils are really contractile. 



Since there is no distinct muscularis mucosa present in the in- 

 testine of Necturus, it is probable that these scattered fibroglia fibrils, 

 arranged either singly, or grouped around the cell protoplasm into 

 structures closely resembling smooth muscle fibers, represent such a layer. 



It is quite probable that in the basement membrane of the kidney 

 tubules, beneath the endothelium of blood vessels and in other places 

 where Mallory found fibroglia fibrils that they are, as he suggests, 

 contractile in character. 



In concluding, I merely wish to emphasize that, as these fibroglia 

 fibrils occur in Necturus, there is no apparent reason for considering 

 them anything other than myofibrils. 



Summary. 



1. In the intestine of Necturus, forming a basement membrane 

 for the lining epithelium and scattered throughout the subepithelial 

 connective tissue, are fibrils which closely resemble the fibroglia fibrils 

 described by Mallory. 



2. These fibrils always, at some point in their course, are in con- 

 nection with the granular protoplasm of the cells from which they 

 arise. In some places, throughout their entire length, the fibrils run 



