CHAP, iv.] THE VASCULAR MECHANISM. 189 



meshwork the irregular spaces of which are occupied by lymph. 

 On the sides of the bundles towards the spaces or between the 

 bundles where these are in apposition, often lying in minute spaces 

 hollowed out in the cement or ground substance uniting the 

 bundles, are found the connective tissue corpuscles. Each of these 

 is a cell consisting of a nucleus, generally oval or elongate, sur- 

 rounded by a protoplasmic cell body usually irregular in form, 

 being sometimes merely spindle shaped but more frequently 

 distinctly branched or stellate, and nearly always much flattened in 

 a plane corresponding to the direction of the fibres, or bundles of 

 the matrix. Although as we have said the nbrillse are cemented 

 together into a bundle, each fibrilla remains sufficiently distinct to 

 have a marked refractive effect on rays of light falling upon or 

 transmitted through the tissue, so that the bundles appear white 

 and opaque ; hence this tissue, and especially a more dense form of 

 it, is sometimes spoken of as white fibrous tissue. Owing to this 

 opacity the more delicate connective tissue corpuscles are not 

 readily visible in the natural condition of the tissue. They may 

 however be brought to view by the action of dilute acid such as 

 acetic acid. Under the influence of this acid each fibrilla swells 

 out, and the swollen fibrillse pressing upon each other cease to 

 refract light so much as before, and thus become more trans- 

 parent, very much as an opaque mass of strips of isinglass becomes 

 transparent when the strips are swollen by boiling ; this increase 

 of transparency allows the corpuscles, which are not swollen but 

 rather shrunken .and made more opaque by the action of the 

 acid, to become visible. The presence of these corpuscles may 

 also be revealed by the use of such staining reagents as while 

 not staining the fibrillated matrix stain the nuclei and the proto- 

 plasmic bodies of the corpuscles. 



Besides these branched irregular flattened connective tissue 

 corpuscles, which do not naturally exhibit any amoeboid movements, 

 leucocytes, exhibiting more or less active movements, are found 

 in the spaces of the tissue, together with corpuscles of a third 

 kind remarkable from the large coarse granules with which the 

 cell substance is studded, and known as " plasma-corpuscles." 



106. When connective tissue is rendered transparent by 

 the action of dilute acetic acid, there come into view besides 

 the corpuscles, a number of fibres, different from the gelatiniferous 

 fibres not only in not being swollen and rendered transparent 

 by the action of the acid, but also by their size, relatively scanty 

 number, clear bold outline and sharply curved course. The fibres 

 vary much in size, some being very fine so as to appear mere lines, 

 while others are very large with a distinct double outline. 

 Whether small or large each fibre is a single fibre, not a bundle, 

 and cannot be split up, like a fibre or small bundle of the ordinary 

 matrix, into fibrillse. Not only is their course sharply curved 

 unlike the gently sweeping outlines of the gelatiniferous fibres, 



