The Relation of Muscle Fibrillae to Tendon Fibrillae etc. 261 



I have presented fig. 10 for the purpose of elucidating certain 

 appearances wliich have been misinterpreted by various investi- 

 gators who have endeavored to establish a continuity between muscle 

 and tendon fibrillae. The figure bears, as can be readily noted, a 

 close resemblanee to some of their published plates. This figure 

 was sketched from a specimen of thigh muscle of an adult white 

 mouse. Both the tendon fibrillae and the muscle fibrillae pursued 

 the same linear direction. lipon the left side of the fibre the sarco- 

 lemma surface {B) at the end of the muscle fibre lay in a plane at 

 exactly a right angle to that of the fibrillae, while on the right 

 side it encountered these structures at an acute angle. These two 

 portions of sarcolemma are uninterruptedly continuous with each 

 other [B — B). The left side of the fibre demonstrates all of those 

 features to which I have previously referred. The tendon fibrillae 

 are separated from the muscle fibrillae by the thickened sarcolemma 

 end. Upon the right side of the fibre the outline of the sarco- 

 lemma because of its obliquity is with much greater difficulty ob- 

 served. Those fibrillae which occupy the same optical plane, for 

 instance, the uppermost aspect of the section, can be seen to be 

 separated from each other by the thin cut edge of the sarcolemma. 

 Those other tendon fibrillae which occupy the middle of the thick- 

 ness of the specimen seem to have perforated that membrane and 

 to have extended into the muscle fibre. This appearance is natur- 

 ally referable to the fact that they are attached to the under sur- 

 face of obliquely inclined sarcolemma and hence underlie the upper- 

 most muscle fibrillae. Their intense red stain, derived from the 

 fuchsin, lends its color, too, to these adjacent overlying muscle 

 fibrillae and, consequently, heightens the Impression that a portion 

 of them extends into the muscle fibre. A careful consideration of 

 the left side of the sketch is sufficient, however, to eradicate all 

 doubt of the discontiuuity of the two kinds of fibrillae. 



The particular criticism that I would raise against 0. Schultze's 

 work in that he has neglected to explain an appearance which is 

 represented in almost every one of his figures, and which is of 

 fundamental importance in our conception of the relation of the 

 sarcoplasm to the sarcolemma. At places he has represented groups 

 of three, four, and more muscle fibrillae which together perforate 

 the sarcolemma and which are then prolonged as tendon fibrillae, 

 i. e., the sarcolemma is interrupted at the point of Perforation of 

 not Single muscle fibrillae but of groups of fibrillae. In other words. 



