142 



STRUCTURE OF MUSCLE. 



The fibre of animal life is recognised from being marked by 

 transverse and slightly waving striae. The fibre of organic life has 

 no transverse striae, and is much smaller than the fibre of animal 

 life. It is polygonal in form or nearly cylindrical, and appears to 

 consist of a number of minute parallel filaments enclosed in a myo- 

 lemma. The most remarkable character of the organic fibre is the 

 existence from point to point of swellings somewhat larger than the 

 diameter of the fibre, and produced by the nuclei of the original 

 nucleated cells from which the fibre was developed. 



The ultimate fibrils are minute beaded filaments in the fibre of 

 animal life, and cylindrical and uniform in the organic fibre. 



According to the researches of Mr. Bowman* the ultimate fibres 

 (primitive fasciculi) are polygonal, a form which is well suited to 

 admit of their being collected into bundles. In size they are very 

 variable, not only in the different classes and genera of animals, 

 but also in the same animal and even in the same muscle. He 

 has observed, moreover, that they are somewhat smaller in the 

 female than in the male ; thus the average diameter of the ultimate 

 fibre in the female, is T | T ; in the male 7 ^ 7 ; the average of 

 both being ^- r In the different classes of animals examined 

 by Mr. Bowman, the largest ultimate fibre was met with in 



fishes, in which the average diameter 

 is ^-z ; next in man ; and then in other 

 classes in the following order : insects, 

 ^5 reptiles, ^fa; mammalia, ^ T ; 

 birds, -^ T . 



The ultimate fibrils (primitive fibrillce) 

 consist of segments separated from 

 each other by constrictions, which 

 give to the entire fibril the appearance 

 of a string of beads. The constric- 

 tions are narrower than the segments, 

 and their component substance is pro- 

 bably less dense than that which forms 

 the segments. An ultimate fibre con- 

 sists of a bundle of fibrils, which are so 

 disposed that all the segments and all 

 the constrictions correspond, and these 

 give rise to the alternate light and dark 

 lines of the transverse strise.f The 

 fibrils are connected together with very 

 different degrees of closeness in different 



* On the Minute Structure and Movements of Voluntary Muscle. By Wm. Bow- 

 man, Esq. From the Philosophical Transactions for 1840. 



F. Transverse section of ultimate fibres of the biceps, copied from the illustrations 

 to Mr. Bowman's paper. In this figure the polygonal form of the fibres is seen, and 

 their composition of ultimate fibrils. 



o. An ultimate fibre, in which the transverse splitting into discs, in the direction of 

 the constrictions of the ultimate fibrils is seen. From Mr. Bowman's paper. 



t According to Gerber the transverse striae on the ultimate fibres are produced by a 

 delicate thread of cellular tissue wound spirally around the ultimate fibrils so as to 

 hold them in a bundle, and my own observations corroborate his. G. 



