Albert C. Eveleshymer 297 



ner, 69, considered it a sheath of connective tissue. Deiters. 61, Bremer, 

 83, and others, have regarded it as a cuticularized portion of the celh 

 F. E. Schnlze, 62, Kolliker, 88, and others, maintain that it is the cell-, 

 membriine. 



The cell-membrane is easily distinguished up to the time the mesen- 

 ch3mie grows in and becomes closely applied to it. Either the cell- 

 membrane is the sarcolemma or the cell possesses no sarcolemma in its 

 earlier stages. 



In the later stages one frequently finds the myoblasts so contracted 

 that their ends have drawn away from one or both septa. In such cases 

 the endomysium and sarcolemma remain attached to the septa, and it is 

 not difficult to discern two entirely different structures; the outer, a 

 fibrous sheath made up of several layers; the inner, a delicate mem- 

 branous sheath which, I believe should be considered as the sarcolemma. 



B. Changes ix the Cytoplasm of the Myoblast. 



CHAKACTER OF FIBRILL^E. METHOD OF FIBRILLATIOX. CHARACTER OF 

 CYTO-RETICULUM. RELATION OF FIBRILLyE TO CYTO-RETICULUM. 



]\Iany and varied have been the hypotheses offered to explain the 

 formation and structure of the fibrillfe. By some of the earlier writers 

 (Deiters, Eouget) they were regarded as extra-cellular products. So far 

 as I am aware no one would now question the generally accepted opinion 

 that they are intra-cellular and are formed in the cytoplasm. It should 

 not be forgotten, however, that Eobin held that they arise from the free 

 ends of the nuclei by a process of gemmation, a view which was later 

 supported by both Eetzius, 81, and Bremer, 83. 



As to the nature of the fibrillfe, there are at least two current views. 

 The first is that in the normal fibres there is neither c3^to-reticulum nor 

 fil)rill?e, these apparent structures found in the fixed tissue being coagu- 

 lation products. This view was ably advocated by Englemann, 70 to 80, 

 and has since been supported by many physiologists. The second is that 

 there are differentiated structures, network or filjrillse, or l)oth, in the 

 living myoblasts. The latter view is that accepted by the greater num- 

 ber of histologists. 



The so-called " network theory "' took its remote origin from the dis- 

 covery by Bowman, 41, that the muscle fibre could be cleft both longi- 

 tudinally and transversely, giving rise to the sarcous elements. Jones, 

 44, and Dobie, 48, held that these elements were united end to end by a 

 cementing su1)stance, while others claimed the existence of a like sulistance 

 between the sides of the sarcous elements. Tlius modified the theory 



