266 W. M. Baldwin, The Relation of Miiscle Fibrillae to Tendon Fibrillae etc. 



Fig. 9. A semi-diagrammatic sketch of a developing intercostal muscle illu- 

 strating the pointed processes of sarcolemma each with its attached 

 tendon fibril. The features of cross-striation of the muscle fibre are 

 wanting at the sarcolemma end. Magnification 1000 diameters. 



Fig. 10. A thigh muscle fibre and tendon of an adult white mouse conforming 

 to type 2. Upon the left side of the figure several inturned processes 

 of sarcolemma are represented in the muscle fibre (Ä). Upon this 

 side the sarcolemma is cut exactly transversely. Upon the right side 

 of the figure the sarcolemma [B] is encountered obliquely by the 

 section knife, consequently the more superficial of the muscle fibrillae 

 are underlaid by the tendon fibrillae. The sarcolemma separates the 

 two structures, still it appears as If the tendon fibrillae extended 

 among the muscle fibrillae having perforated the sarcolemma. Magni- 

 fication 1000 diameters. 



Fig. 11. This is a portion of a muscle fibre from a caudal muscle of a tad- 

 pole 1,5 cm long. The presence of the richly granulär protoplasmic 

 mass imbedding a nucleus and surrounding the muscle fibrillae may 

 be taken as an indication that the muscle fibre is in a developmental 

 stage. In the adult state such protoplasmic masses are wanting. 

 The membrane {B] investing the mass may be provisionally inter- 

 preted as the sarcolemma. The presence of the line continuous with 

 the sarcolemma and carried across the fibre end does not represent 

 the fibre end. I have elucidated this appearance upon a previous 

 page (4). The sarcolemma proper is drawn out into a number of 

 processes in which the muscle fibrillae end and upon whose apex a 

 tendon fibril is inserted. Magnification 1500 diameters. 



