The Relation of Muscle Fibrillae to Tendon Fibrillae etc. • 253 



throiigli tlie medium of this tendon-investing-, connective tissue sheath, 

 or peritendinum, comparable to the periosteum in the above instance, 

 do the muscle fibres establish their connectiou with the tendon. 

 The matter involved then is a consideration rather of the relation 

 of the muscle fibrillae to the peritendinum (Peritenonium) fibrillae. 



A similar instance of a muscle fibre of tbis type with its attached 

 tendon is represented in fig. 5 under a magnification of 1500 dia- 

 meters. The peritendinum, consisting of several layers of connective 

 tissue fibres and cells, separates the obliquely-inclined muscle fibre 

 from the tendon. Due to a tear in the tissues an interval exists 

 between a portion of the muscle fibre and the peritendinum and 

 another between the latter and the tendon. In the rest of their 

 extent however, the various structures have maintained their proper 

 relationship to each other. The figure demonstrates five muscle 

 fibrillae {Ä), which proceed directly up to the sarcolemma without 

 losing their features of cross-striation, such as was the case ob- 

 served with the mouse and chicken extrinsic eye muscles. The 

 tendon end of the sarcolemma is very noticeably thickened and 

 presents upon its internal surface several small elevations upon each 

 of which a muscle fibril is inserted. Sections staiued with picro- 

 fuchsin demonstrate that such elevations belong to the sarcolemma 

 rather than to the muscle fibrillae. Moreover, sections stained with 

 hematoxylin-fuchsin indicate that the sarcolemma, with these ele- 

 vations has a diflferent staining reaction from that of the peritendinum, 

 and that both of these diflfer from the tendon. Morphologically there 

 is no evidence that the sarcolemma is any other than a homo- 

 geneous structure unperforated and untraversed by any formed 

 fibrillae. With differential staining it appears as a thickened homo- 

 geneous, unstriated, and non-fibrillar membrane. Nor is there any 

 evidence of the peritendinum fibrillae turning at an angle to per- 

 forate it. 



Another instance of the general type of muscle termination as 

 demonstrated in figs. 1, 2, and 3 is furnished by the caudal muscu- 

 lature of the tadpole. A portion of a muscle fibre with its attached 

 tendon fibrillae is represented in fig. 6. This fibre was removed 

 from a tadpole about 5,0 cm long. The sarcolemma is very thin 

 and is seen in the figure to be drawn out into a number of cone- 

 shaped processes. Into each of these prolongations as many as 

 from ten to forty muscle fibrillae enter and, without suff'ering any 

 reduction in diameter or losing their features of cross-striation, 



