CONNECTIVE TISSUE 



6 7 



of very coarse elastic fibers with very little white fiber. It is therefore com- 

 monly used for the histological and chemical study of elastic tissue (Fig. 

 54, B and C). In man the stylohyoid ligament and the ligamenta flava 

 are of this class, and they exhibit the yellowish color which is character- 

 istic of elastic tissue. Elastic fibers are found also in the ground substance 

 of certain cartilages, which will be described later. 



Connective Tissue Cells. In addition to white collagenous fibers and 

 yellow elastic fibers, connective tissue contains cells and intercellular 

 spaces. The cells which produce fibers are known as fibroblasts (/JAao-ros, 

 a bud, is used in many terms to indicate a formative cell, with a prefix 

 which usually designates the structure which it produces). Actively 



FIG. 54. ELASTIC FIBERS. 



A, Network of thick elastic fibers below, passing into a fenestrated membrane above. From the human 

 endocardium. B, Thick elastic fibers (f) from the ligamentum nuchae of the ox; b, white fibers.^C, 

 Cross section of the ligamentum nuchae, lettered as in B. 



growing fibroblasts, both in the embryo and in the adult, exhibit fibroglia 

 fibrils at their borders, but in mature connective tissue these fibrils are 

 seldom found. The cells of fully formed connective tissue are generally 

 flattened or lamellar, consisting of a thin pale layer of almost homogeneous 

 protoplasm, which is sometimes vacuolated. Such cells when seen on 

 edge are spindle-shaped. They may be spread out in flat layers, retaining 

 the protoplasmic connections characteristic of mesenchyma, as seen in the 

 mesentery (Fig. 55, c). In dense connective tissue the cells also exhibit 

 broad thin protoplasmic processes (Fig. 56, c), but they have become more 

 or less detached from one another. The cells are bent to conform with 

 the adjacent fibers, to which they are closely applied, and along which, 

 in living tissue, they have been observed to migrate. The nuclei of these 

 cells are elliptical on surface view, and rod-shaped when seen on edge. 

 They contain fine chromatin granules, and sometimes a small but distinct 

 nucleolus. Occasionally the nuclei are indented on one side. The centro- 



