TENDONS 



117 



of successive cells are often so placed as to be immediately adjacent. Ac- 

 cording to Loevy the fibrils are developed from fibroblasts ; the definitive 

 tendon cells, which form the primary bundles, arise from cells of Ran- 

 vier. Both come from mesenchyme cells, but the fibroblasts entirely 

 disappear, while the cells of Ranvier persist as the characteristic winged 

 tendon cells. 



Ligaments, fascia, and aponeuroses are very 

 similar to tendon, but are less compact and contain 

 more elastic tissue. 



Bursae are mesothelium-lined sacs in connec- 

 tion with the large diarthroses and certain locations 

 where tendons are subject to friction. 



Tendons are supplied with blood-vessels and 

 sensory nerve endings, in a manner very similar to 

 skeletal muscle. 



The exact manner of the attachment of striped 

 muscle to tendon is still disputed. According to 

 certain investigators (0. Schultze, Arch. f. mikr. 

 Anat., Bd. 79, 1912), the myofibrils and tendon 

 fibrils are directly continuous through the sarco- 

 lemma. Others (Baldwin, Morph. Jahrb., Bd. 45, 

 1912) hold that the muscle ends sharply, remain- 

 ing striped to its termination, and that the rounded 

 or pointed end is completely enveloped by the sar- 

 colemma (Fig. 132). The muscle fibers are de- 

 scribed as being dovetailed into the tendon, the ten- 

 don fibrils being attached to the sarcolemma. This 

 is the more commonly accepted interpretation; but 

 it seems probable that both types of muscle-tendon 

 connections occur in different muscles, for in cer- 

 tain muscles the cross striations become gradually 

 more vague toward the tendon, and the point of 

 transition from muscle to tendon is by no means sharply marked. More- 

 over, the fact that certain ligaments and aponeuroses arise normally by 

 transformation of muscle adds support to the idea of muscle-tendon con- 

 tinuity. 



Baldwin distinguishes two general types of muscle termination with 

 respect to tendon : one in which the long axes of tendon and muscle 

 fiber coincide; a second in which they meet at an angle. In neither type 

 does he recognize a direct continuity between muscle and tendon fibrils. 



FIG. 132. PORTION 

 OF A MUSCLE FI- 

 BER FROM THE TAIL 

 OF A 5 CM. FROG 

 TADPOLE. 



Each cone-shaped 

 sarcolemma process 

 has attached to it a 

 tendon fibril. Two 

 of the processes do 

 rive fibrillae from a 

 large fibroblastic cell 

 situated among the 

 tendon fibrilte. (Af- 

 ter Baldwin.) xiooo. 



