THE CONNECTIVE TISSUES. IO5 



and intercross in all directions, as where areolar tissue is found in 

 larger quantity. (Fig. 70.) 



(&) Tendons, aponeuroses, and ligaments represent the densest 

 variety of fibrous connective tissue, and are composed almost 

 wholly of white fibrous tissue. This is found in the form of rela- 

 tively large bundles of white fibrils, having a parallel or nearly 

 parallel course. In tendons these bundles are known as primary 

 tendon bundles or tendon fasciculi. The fibrils of white fibrous con- 



Fibrils. - 



Nucleus. --- 



Fig. 70. Fibrous connective tissue (areolar) from the great omentum of the rabbit ; 



X400. 



nective tissue forming the fasciculi are cemented together by an in- 

 terfibrillar cement substance. Here and there the fasciculi branch 

 at very acute angles and anastomose with other fasciculi. The fas- 

 ciculi are grouped into larger or smaller bundles, the secondary 

 tendon bundles, which are surrounded by a thin layer of areolar con- 

 nective tissue, and in part covered by endothelial cells. Between 

 the tendon fasciculi there is found a ground-substance, interfascicu- 

 lar ground-substance, identical with the ground-substance in areolar 

 connective tissue. In this there are cell-spaces occupied by the 

 tendon cells, morphologically similar to the branched cells of areolar 

 connective tissue. The tendon cells are arranged in rows between the 

 tendon fasciculi. They have an irregular, oblong body, containing 

 a nearly round or oval nucleus. Two, three, or even more wing- 

 like processes (lamellae) come from the cell-body and pass between 

 the tendon fasciculi. In cross-section the tendon cells have a 

 stellate shape. 



The secondary tendon bundles are grouped to form the tendon, 

 and the whole is surrounded and held together by a layer of areolar 

 connective tissue, called the peritendineum. From this, septa pass in 

 between the secondary tendon bundles, forming the internal peri- 

 tendineum. The blood- and lymph-vessels and the nerve-fibers 

 reach the interior of the tendon through the external and internal 

 peritendineum. 



