260 W. M. Baldwin 



processes. This fact alone speaks most positively against a Perfo- 

 ration of the sarcolemma hy the tendon fibrillae and their subsequent 

 passage through the muscle fibre to meet and fuse with the muscle 

 fibrillae. Moreover, there are at first no tendon fibrillae attached to 

 the sarcolemma end in the intervals between the cone-like processes, 

 whereas the muscle fibrillae, undifferentiated in structure are almost 

 from the very first already attached to the internal surface of the 

 sarcolemma at such corresponding intervals. 



A Word should be said about the combination of fuchsin S with 

 alcoholic-hematosylin as recommended by several investigators. I 

 have used these stains upon many of my own preparations, with the 

 result that, dependent upon the relative concentration of the former 

 constituent and the time of exposure, I was able to stain with the 

 fuchsin not only the tendon fibrillae but also that portion of the 

 terminal undifferentiated muscle fibrillae lying adjacent to and atta- 

 ched to the sarcolemma end. Indeed, by carrying the staining a 

 little fuither I was able to stain the neighboring portions of the 

 muscle fibrillae which presented all of the features of eross-striation. 

 Hence, this combination of stains seems to be most unreliable as a 

 criterion of morphological values. 



For the developmental and morphological reasons which I have 

 enumerated above, the assertion, that these ends of undifferentiated 

 muscle fibrillae, by reason of their staining reactions, represent ten- 

 don fibrillae which have perforated the sarcolemma in order to join 

 the muscle fibrillae, cannot be accepted as convincing to say nothing 

 at all about being most positively denied. Yet some of the publi- 

 shed figures intended to represent the continuity of these two kinds 

 of fibrillae and stained with the same stains give exactly this same 

 appearance. 



In order to be positive that the cone-shaped extremities of the 

 sarcolemma end were not the result of shrinkage of the tissue in 

 the course of its preparation, I studied specimens of living muscle 

 under high magnifications and ascertained that these processes were 

 characteristic of the termination of the muscles conforming to the 

 first type of ending. I found also that the presence of a uni- 

 formly rounded sarcolemma end such as has been figured by other 

 investigators may be accepted as proof positive that the actual end 

 of the muscle fibre has not been represented. I shall have occasion 

 to refer to this feature in connection with fig. 11 upon a subsequent 

 page. 



