302 



MANUAL OF HISTOLOGY. 



Foetal muscle, as already remarked, contains glycogen, but at first, before 

 the embryonic cells have begun to undergo their characteristic transfor- 

 mation into fibres, this substance is entirely absent, according to the 



interesting investigations of Ber- 

 nard and Kuhne. In smooth 

 nucleated fibres it presents itself 

 as a granular matter deposited 

 around the nucleus. Rouget, how- 

 ever, asserts that it only occurs 

 diffusely. Later on, with the de- 

 velopment of the transverse striae 

 and appearance of the characteristic 

 muscular structure, the fibre is in- 

 filtrated with glycogen, which per- 

 sists until birth, disappearing 

 rapidly on the commencement of 

 respiration. 



As yet we have not said one word 

 as to the origin of the structure- 

 less envelope, the sarcolemma. In 

 earlier years, supposing the for- 

 mative cell to be endowed with 

 an envelope, this sarcolemma was 

 looked upon very generally as be- 

 ing the metamorphosed cell-mem- 

 brane of the former. But now 

 that we have convinced ourselves 

 that no such envelope exists upon 

 the formative cell, such a view can 

 no longer be entertained. At the 

 present we find two theories very 

 generally held in regard to this 

 point. According to one, the sar- 

 colemma is a hardened secretion 

 from the cell, of the same nature 

 as the so-called cuticular forma- 

 tions ; according to the other (and 

 we are inclined to favour this 



View) this Structureless sheath is 



a connective-tissue formation laid 



down On the muscle fibre from 

 . . , i i i j 



Without, which may be Compared 



f n f^p P l aC ;fip linn n diner lavPTN of 



many connective-tissue structures. 

 That the end of the muscle fibre can be separated with its envelope 

 from the tendon, as we have seen at p. 294, appears to us to be no very 

 weighty objection to this view. Do we not also see elastic fibres sepa- 

 rating themselves from connective-tissue bundles] and yet they have both 

 the same origin. 



The branching muscular elements of the heart correspond, we are assured 

 by Koelliker, each to a metamorphosed stellate cell, and the whole to a 

 cellular network. Weismann, however, is opposed to this theory from his 

 own observations. In his opinion the muscular bands consist (and of 



Fis: 29.'). Development of striped muscle fibres 



tion; c, d, portion of a somewhat more mature 

 fibre, with numerous nuclei and considerable dia- 

 meter; ,/,?, fibres still further developed, with 

 nuclei in the axis ; h. nuclei beneath the enve- 

 lope; t, a fibre breaking up into thick discs. 



