

STRIATED MUSCULAR FIBRE. 



199 



Bowman estimates the average diameter of the fibres in the Human 

 male at l-352d of an inch ; the largest being l-192d, and the smallest 

 l-507th. In the female, he found the average to be l-454th of an inch ; 

 whilst the largest was l-384th, and the smallest l-615th. The average 

 size of the Muscular fibre is greater among Reptiles and Fishes, than 

 in other Vertebrata ; but, on the other hand, the extremes are much 

 wider. Thus its dimensions vary in the Frog from l-100th to 1-1 000th 

 of an inch ; and in the Skate from l-65th to l-300th. 



335. When the striated Muscular Fibre is examined still more closely, 

 it is found to contain an assemblage of very minute elements, which 

 appear to be flattened disk-like cells, of very uniform size. These 

 primitive particles are adherent to each other both by their flat surfaces, 

 and by their edges. The former adhesion is usually the most powerful, 

 and causes the substance of the fibre, when it is broken up, to present 

 itself in the form of delicate fibrillce, each of which is composed of a 

 single row of the primitive particles (Fig. 60). On the other hand, the 

 lateral adhesion is sometimes the stronger, and causes the fibre to break 

 across into disks, each of which is composed of a layer of the primitive 



Fig. 60. 



Striated muscular fibre separating into fibrillae (from a Terebratula). 



particles (Fig. 61). That the fibre is a solid collection of these elemen- 

 tary parts, and not hollow in the centre, as some have supposed, is 

 shown by making a thin transverse section of a fasciculus (Fig. 62) ; by 

 which also the polygonal form of the fibre is made apparent. 



Fig. 61. 



Fig. 62. 



An ultimate fibre, in which the 

 transverse splitting into disks, in 

 the direction of the striation of 

 the ultimate fibrils, is seen. 



Transverse section of ultimate fibres of 

 the biceps. In this figure the polygonal 

 form of the fibres is seen, and their com- 

 position of ultimate fibrils. 





336. When the fibrillse are separately examined, under high magm- 

 inz Dower, they are seen to present a cylindrical or slightly-beaded 



fying power, they are seen to present a cyli 



