TENDON. 



49 



of partitions or septa. This ordinary connective tissue contains nerves 

 which supply the tendon, to be further described on page 103; also blood 

 vessels in relatively small number, and lymphatic vessels which are 

 confined to the outer sheath. The septa surround bundles or fasciculi 

 of tendon fibers, called "secondary tendon bun- 

 dles" in distinction from the smaller "primary 

 bundles" of which they are composed. The latter 

 are groups of fibers more or less definitely sur- 

 rounded by wing-like processes of the tendon cells, 

 which appear as dots in Fig. 50, but are clearly 

 shown in Fig. 51. The tendon cells are charac- 

 terized by their compressed branches which extend 

 between and around the fiber bundles, anastomos- 

 ing with similar branches of neighboring cells. 

 The fibers are white, consisting of collagen (the 

 gelatin-producing substance) and of tendo-mucoid 

 which may be found in the cementing matrix. 

 Elastic elements are said to occur in small quan- 

 tity especially near the cells and their processes. 

 Intercellular spaces are very small and are not 

 shown in the figure. In longitudinal sections, Fi" 



o o ' O 



52, the parallel arrangement of the fibers is ap- 

 parent, and the nuclei are in rows. The protoplasm is often indistinguish- 

 able, but in special preparations from delicate tendons it appears as a 

 thin folded layer with plate-like projections. Fig. 53. 



FIG. 51. FROM THE CALCA- 

 NEAN TENDON (TENDO 

 ACHILLIS) OP A RABBIT. 

 (After Prenant.) 



p. b., Primary bundle;* sh., 

 sheath of the bundle ;| p., 

 process from a tendon 

 cell, t. c., extending into 

 a primary bundle. The 

 entire figure is a portion of 

 a secondary bundle. 



FIG. 52. LONGITUDINAL SECTION OF A CALCA- 

 NEAN TENDON OF MAN. 



FIG. 53. TENDON CELLS FROM THE TAIL OP 

 A RAT. STAINED WITH METHYLENE BLUE, 

 IXTRA VITAM. (Huber.) 



The fibrous sheath, vagina fibrosa, which surrounds the tendon, may 

 contain a cavity filled with fluid. Such a tendon sheath is called a mucous 

 sheath, vagina mucosa. The cavity arises as a cleft in the embryonic 

 connective tissue and its walls are formed of mesenchymal epithelium. 

 The cells have become flattened and the fibers felted together to bound 



