344 THE SOLIDS. 



are obtained, and this cleavage is just as natural, though less 

 frequent, than the former. Hence it is as proper to say 

 that the fibre is a pile of discs as that it is a bundle of 

 fibrilla? : but, in fact, it is neither the one nor the other, but 

 a mass in whose structure the^e is an intimation of the ex- 

 istence of both, and a tendency to cleave in the two direc- 

 tions. If there was a general disintegration along all the 

 lines in both directions, there would result a series of particles, 

 which may be termed primitive particles, or sarcous elements, 

 the union of which constitutes the mass of the fibre. These 

 elementary particles are arranged and united together in two 

 directions. All the resulting discs as well as fibrillai are 

 equal to one another in size, and contain an equal number 

 of particles. The same particles compose both. To detach 

 an entire fibrilla is to abstract a particle of every disc, and 

 vice versd. The width of the fibre is therefore uniform, and 

 is equal to the diameter of any one of its fibrilla, and is 

 liable to the greatest variety." 



This view of the structure of the striated muscular fibre is 

 ingeniously conceived and well expressed; nevertheless it can 

 be shown, I think, notwithstanding its ingenuity, to be in- 

 correct. 



There are two considerations which appear to me to be 

 sufficient to disprove the view just propounded. The first is, 

 that the rudimentary muscular fibre consists of one or more 

 threads or fibrillae, containing imbedded in them a number of 

 elongated nuclei, which, however, have no correspondence 

 with the transverse markings ; and the second is, that, while 

 any muscular fibre may at any time be readily separated into 

 its component fibrilke, the simultaneous transverse cleavage 

 spoken of and figured by Mr. Bowman is an occurrence of 

 extreme rarity, and one, moreover, of which I have never 

 been able to perceive the slightest trace in any muscular fibre 

 which has fallen under my notice. 



It would thus appear that the older view is the correct 

 one, and that the striped muscular fibre is made up, as al~ 

 ready described, of a variable number of fibrillas enclosed in 

 a tubular sheath. 



Blood Vessels of Muscles. Muscles are copiously supplied 



