The Eelation of Muscle Fibrillae to Tendon Flbrillae etc. 259 



are no peritendinum fibrillae intervening between the tendon and the 

 obliqaely-placed muscle fibres. Explaining upon developmental 

 grounds the presence of the sarcolemma infoldings into the muscle 

 fibre, and ascertaining through staining reactions the identity of 

 these infoldings in the adult with the sarcolemma, and, in addition, 

 by the same methods most positively establishing the morphological 

 differences between such structures and the muscle and tendon 

 fibrillae, and moreover, failing to observe any turning of the tendon 

 fibrillae at an obtuse angle, as would be necessary to establish con- 

 tinuity with the muscle fibrillae, we are in a position here, as well, 

 to deny in this type of muscle the continuity of tendon fibrillae with 

 muscle fibrillae. 



Regarding those other muscles which conform to the first type 

 of termination, where the linear direction of the tendon fibrillae in 

 the adult corresponds to that of the muscle fibrillae, it must be con- 

 fessed that the problem is not so readily solved, the answer, ho- 

 wever, can just as positively be given. The chief difficulty encoun- 

 tered is the exceeding thinness of the sarcolemma and the overlying 

 and underlying of tendon and of muscle fibrillae in vertical optical 

 planes upon the obliquely inclined surfaces of sarcolemma- end pro- 

 cesses. The two kiuds of fibrillae accordingly lie closer together. 



The facts pointing strongly against continuity in this type of 

 muscle are, — each sarcolemma process has attached to it but a Single 

 connective-tissue fibril, yet from ten to forty muscle fibrillae termi- 

 nate in the respective process. A reduction in diameter of each 

 muscle fibril is not demonstrable, such as must be the case if conti- 

 nuity with the Single attached tendon fibril existed. Furthermore, 

 there is no indication of a change in direction of the muscle fibrillae 

 at the sarcolemma end in order to join the Single apically-attached 

 tendon fibril. The sarcolemma of the process is not thickened as 

 one might expect to find, if the numerous muscle fibrillae turned 

 and passed along its surface or through its substance in order to 

 reach the tendon fibril. Again, the differences in size of the tendon 

 fibrillae are not correlative to the variations in size of the sarcolemma 

 processes or to the number of muscle fibrillae therein terminating. 

 Further, the Single tendon fibrillae can be traced up to a connective 

 tissue cell body, a fact suggestive of their genesis. The staining 

 reactions pröve that such fibrillae pass only up to the sarcolemma 

 end. In addition, in adult muscles the cross-striation proceeds di- 

 rectly up to the internal surface of the cone-shaped sarcolemma 



17* 



