258 W. M. Baldwin 



When the directiou of the two coincide, the muscle fibre of the 

 adult retains it8 earlier developmental features to the extent that 

 the sarcolemma end still preserves its cone-shaped blunt projections 

 into which the muscle fibrillae, presenting all of their features of 

 cross-striation, enter to fuse with its internal surface. These sarco- 

 lemma projections with their intervening recesses are dovetailed into 

 corresponding features of the tendon extremity. The second general 

 type of muscle end is observable in those other muscles where the 

 long axis of the tendon meets that of the muscle fibre at an angle. 

 This form is to be regarded as a developmental derivative of a con- 

 dition which in the younger specimens conformed to the type of 

 structure which we have designated under I. So far as my own ob- 

 servations have led me I have not yet seen a developing muscle 

 fibre which did not conform to the first type. 



In other words, before the muscle fibre has grown far enough 

 to reach its definitive oblique Insertion it terminates in cone-shaped 

 sarcolemma processes which give attachment to tendon fibrillae whose 

 direction corresponds to the long axis of the muscle fibre itself. 



Those muscles conforming to the bipenniform type of arrange- 

 ment present the most positive evidence against a continuity of 

 muscle fibrillae with tendon fibrillae, since in these a layer of dense 

 connective tissue, the peritendinam, intervenes and separates the two 

 structures from each other. The features to be considered with 

 especial care in these muscles, therefore, are the peritendinum 

 fibrillae and the muscle fibrillae. Continuity between the latter and 

 the tendon fibrillae is absolutely out of the question. The presence 

 of the greatly thickened sarcolemma end whose homogeneous nature 

 can be very readily made out with a magnification of 1500 dia- 

 meters, renders possible the most definite answer to the question 

 of continuity so far as these muscles are eoncerned. In no instance 

 is there the slightest indication of a fibrillar structure perforating 

 this homogeneous membrane. There is surely no turning of the 

 peritendinum fibrillae observable as must be the case were conti- 

 nuity to be established with the obliquely lying muscle fibrillae. 

 We are in a position , therefore , so far as these muscles of the 

 adult are considered, to corroborate most completely the views of 

 Ran VIER, Weismann, Kölliker and Motto-Coca, that no conti- 

 nuity exists between the tendon fibrillae and the muscle fibrillae. 



The same conclusions may be drawn as well in the instance of 

 those other muscles conforming to this general type where there 



