The Relation of Muscle Fibrillae to Tendon Fibrillae etc. 255 



of the cone-shaped sarcolemma processes upon which they are inserted 

 nor with tbe number of muscle fibrillae wbich terminate in such 

 sarcolemma processes. 



Apart from these considerations, however, the staining reactions 

 demoDStrate very clearly that tbe tendon fibrillae pass only up to 

 the sarcolemma. They do not penetrate it, neitber do the muscle 

 fibrillae. Tbe tbickness of tbe sarcolemma everywbere separates 

 the two structures from each other. 



Further evidence is contributed by the developing intercostal 

 muscles wbich I have studied, and of wbich I have sketched three 

 fibres in figs. 7, 8, and 9. In figure 7 each of the three pointed 

 extremities of tbe sarcolemma has a connective tissue fibril attacbed 

 to its apex. The fibril on the right is seen to be derived from a 

 distinet cell body wbich encloses a relatively large nucleus. The 

 Clements of cross-striation do not accompany tbe muscle fibrillae up 

 to the extreraity of tbe sarcolemma. In the vicinity of tbe latter 

 these fibrillae somewhat resemble the tendon fibrillae in morpho- 

 logical characters, yet there is no morphological appearance to be 

 noted from wbich it might be inferred tbat the homogeneous sarco- 

 lemma is perforated by the passage of eitber form of fibril. Tbe 

 staining of tbe section shows, in addition, tbat whereas the muscle 

 fibrillae are tbin and very faintly stained, tbe tendon fibrillae in 

 these instances are relatively deeply stained and much thicker. At 

 no place have I seen tbese tendon fibrillae inside of the sarcolemma 

 as SCHüLTZE has represented in bis figures. 



Fig. 9 represents somewhat semidiagrammatically the typical 

 muscle termination observed in these developing muscles. The 

 termination of the muscle fibre as a whole is seen to be bluntly 

 pointed, biit the sarcolemma end is observed, in addition, to present 

 upon close examination with a high power very many small cone- 

 shaped processes to each of wbich a connective tissue fibril is at- 

 tached. Tbe younger the muscle fibre, the smaller are these pro- 

 cesses and the less the numbre of muscle fibrillae terminating within 

 each of them. In tbe course of development as tbese processes 

 increase in size and the number of contained muscle fibrillae par- 

 takes of a proportional increment, but a Single tendon fibril, not- 

 withstanding, is found to be attached to the apex of these processes, 

 in other words tbese apical fibrillae do not multiply in this type 

 of muscle. Herein lies another significant fact denying the con- 

 tinuity of tendon fibrillae with muscle fibrillae. 



