On a system of fibre-cells. 537 



Of the fibre cells which enter intimately into the constitution of 

 the perivascular condensation, there are (a), A number of elongate 

 oval fibre-cells which alike by their conspicuous appearance (Fig. 4 

 and 3 a) and by the clearness of their staining- stand out in a wonder- 

 ful manner. Their long axis is parallel to that of the vessels. They 

 lie in the ground substance bordering the vessel and in favourable 

 specimens — when too many are not stained — their processes can 

 be followed up and down along the vessel for enormous lengths. 



A fewer and shorter number of their processes radiate outwards 

 and pass into the general ground-substance (cf Figs. 2, 3, and 4 a). 



These cells lie at moderate distances from one another (Fig. 2), 

 and in a well stained specimen the ensemble of their longitudinal 

 processes apparently lying on the vessels surface, give to the latter 

 the appearance of a fine longitudinal surface — striation. These fibres 

 are slightly wavy in theü' com-se, they do not branch or anastomose 

 but run independently from cell-body to their termination. The slightly 

 oblique direction of several of these in their mainly longitudinal course 

 serves to produce the appearance of a loose open meshwork on the 

 surface of the vessels, the meshes appearing mainly elongated longi- 

 tudinally somewhat after the fashion of the meshes covering the lower 

 part of a balloon (see Fig. 2 and 5). 



Intimately intermixed with these can be seen a number of cells 

 which are (b) elongated transversely to the direction of the vessel; and 

 are therefore best seen around transverse sections of the vessels 

 (Fig. 3 h and 2 a). These cells are present in smaller numbers than 

 the longitudinal cells. In the smaller vessels of the cortex their fibre- 

 processes almost completely surround the vessel, while in medium sized 

 vessels they circle round for % oï" Vi ^^^^ ^'^J i^^S- 3 ^), forming a 

 system of embracing fibres (c£ also Fig. 5). 



The above two sorts of cell-elements being intimately interwoven, 

 fonn a feltwork imbedded in the ground sidjstance immediately sur- 

 rounding the vessel. They have no community or continuity with the 

 adventitial sheath, for the adventitial sheath lies with the muscularis 

 and intima outside the groundsubstance. 



The meshes of the felted slieatli thus formed, are exceeding fiiie 



