MUSCLE. 341 



duced by the winding of a filament around it, but rather of 

 a line formed by the apposition of a series of dots or shorter 

 lines ; in which manner, indeed, it is that the striation of the 

 fibre is really produced, as we have seen. 



The fibrillae contained in each fibre are unbranched, of 

 great tenuity, of nearly equal diameter (see Plate XLIL 

 fig. 1.), and their number varies greatly, amounting in the 

 larger fibres to as many as fifty or sixty, while in the smaller 

 they may not exceed from one to five and upwards, according 

 to the breadth of the filament. 



The striae present a very uniform and strongly marked 

 character : the spaces between them are not, however, equal : 

 thus, they are sometimes rather longer than the diameter of the 

 fibrilla : at other times, they are shorter, and when the stria} 

 are very close, the fibrilla becomes ventricose or moniliform. 



Much difference of opinion prevails as to the nature of the 

 striation exhibited by the fibrillae. Drs. Sharpey * and 

 Carpenter f incline to the opinion that each fibrilla consists 

 of a series of particles or cells cohering in linear series, and 

 that the lines indicate the point of junction of these ; Mr. 

 Erasmus Wilson \ attributes a still more complicated struc- 

 ture to the striated fibrilla. He believes that two kinds of 

 cells exist in each fibrilla ; a pair of light cells separated by a 

 delicate line, being interposed between each pair of dark 

 ones. 



Lastly, Bowman considers that the lines indicate the 

 divisions between particles, which he denominates " sarcous 

 elements." 



My own view of the nature of these lines differs from that 

 of all the gentlemen named. I consider that the lines in 

 question are produced by the simple corrugation or wrinkling 

 of the threads at regular distances : a view, the accuracy of 

 which is all but proved by a consideration of the development 

 of muscular fibre, and by the action of acetic acid on the 

 fibrillae of the heart, the transverse markings of which it en- 

 tirely obliterates. 



* Quain's Anatomy, 5th edition, vol. ii. p. 168. 



f Human Physiology, p. 176. 



j Manual of Anatomy, 3d edition, p. 16 . 



