30 HAND-BOOK OF PHYSIOLOGY. 



which some of them are probably identical. They consist of finely gran- 

 ular nucleated protoplasm, and have the property, not only of changing 

 their form, but also of moving about, whence they are termed migra- 

 tory. They are readily distinguished from the branched connective-tissue 

 corpuscles by their free condition, and the absence of processes. Some 

 are much larger than others, and are found especially in the sublingual 

 gland of the dog and guinea pig and in the mucous membrane of the 

 intestine. A second variety of these cells called plasma cells (Waldeyer) 

 are larger than the amoeboid cells, apparently granular, less active in their 

 movements. They are chiefly to be found in the inter-muscular septa, 

 in the mucous and submucous coats of the intestine, in lymphatic glands, 

 and in the omentum. 



Intercellular Substance. This may be fibrillar, as in the fibrous 

 tissues and certain varieties of cartilage; or homogeneous, as in hyaline 

 cartilage. 



FIG. 26. FIG. 27. 



FIG. 26. Flat, pigmented, branched, connective-tissue cells from the sheath of a large blood-ves- 

 sel of frog's mesentery: the pigment is not distributed uniformly through the substance of the larger* 

 cell, consequently some parts of the cell look blacker than others (uncontracted state). In the two 

 smaller cells most of the pigment is withdrawn into the cell-body, so that they appear smaller, black- 

 er, and less branched, x 350. (Klein and Noble Smith.) 



FIG. 27. Fibrous tissue of cornea, showing bundles of fibres with a few scattered fusiform cells 

 lying in the inter-fascicular spaces. X 400. (Klein and Noble Smith.) 



The fibres composing the former-are of two kinds (a.) White fibres. 

 (b.) Yellow elastic fibres. 



(a.) White Fibres. These are arranged parallel to each other in wavy 

 bundles of various sizes: such bundles may either have a parallel arrange- 

 ment (Fig. 27), or may produce quite a felted texture by their interlace- 

 ment. The individual fibres composing these fasciculi are homogeneous, 

 unbranched, and of the same diameter throughout. They can readily 

 be isolated by macerating a portion of white fibrous tissue (e.g., a small 

 piece of tendon) for a short time in lime, or baryta-water, or in a solution 

 of common salt, or potassium permanganate: these reagents possessing 

 the power of dissolving the cementing interfibrillar substance (which is 

 nearly allied to syntonin), and thus separating the fibres from each other. 



(b.) Yelloiu Elastic Fibres (Fig. 28) are of all sizes, from excessively 

 fine fibrils up to fibres of considerable thickness: they are distinguished 



