286 



MUSCULAR TISSUE. 



Fasciculi. The fasciculi are of a prismatic figure, and their sections have 

 therefore an angular outline (fig. 322). The number of fibres of which they consist 

 varies, so that they differ in thickness, and a large fasciculus may be divisible into* 

 two or three orders of successively smaller bundles, but of no regularly diminishing 

 magnitude. Some muscles have large, others only small fasciculi ; and the coarse 

 or fine texture of a muscle, as recognized by the dissector, depends on this circum^ 



Fig. 322. A, SMALL PORTION OF MUSCLE, CONSISTING OF LARGER AND SMALLER FASCICULI, NATURAI/ 



SIZE ; B, THE SAME MAGNIFIED 5 DIAMETERS, SHOWING A TRANSVERSE SECTION. (Shatpey.) 



Fig. 323. A FEW MUSCULAR FIBRES, BEING PART OF A SMALL FASCICULUS, MORE HIGHLY 



MAGNIFIED. (Sharpey.) 

 b, b, fibres ; a, end view ; c, a fibre splitting up into longitudinal elements. 



stance. The length of the fasciculi is not always proportioned to the length of the 

 muscle, but depends on the arrangement of the tendons to which their extremities 

 are attached. When the tendons are limited to the ends of a long muscle, as in the 

 sartorius, the fasciculi, having to pass from one extremity to the other, are of great 

 length ; but a long muscle may be made up of a series of short fasciculi attached 

 obliquely to one or both sides of a tendon, which advances some way upon the 

 surface or into the midst of the fleshy part, as in the instances of the rectus muscle 

 of the thigh, and the tibialis posticus. Many short fasciculi connected thus to a 

 long tendon, produce by their combined operation a more powerful effect than a few 

 fasciculi running nearly the whole length of the muscle ; but by the latter arrange- 

 ment the extent of motion is greater, for the points of attachment are moved through 

 a longer space. 



Fibres ; their figure and measurement. In shape the fibres are cylindrical 

 or prismatic with rounded angles. Their diameter varies greatly even in each 

 muscle, although for the most part a prevailing standard is found to exist in every 

 muscle. The largest fibres in human muscles average about -^^ inch (O'l mm.) in 

 diameter, the smallest are only about one-tenth that width. 



The eye-muscles are mainly composed of small fibres ; and the muscles of the limbs mainly 

 of larger ones, but there is no constant relation between the size of a muscle and that of its 

 constituent fibres. The fibres tend to be thicker in the male than in the female (for the same 

 muscles) ; the differences between different muscles are not evident in infancy, but only mani- 

 fest themselves in the process of growth (Schwalbe and Mayeda). 



The fibres composing a muscle are of limited length, generally not exceeding one 

 inch and a half ; and accordingly in a long fasciculus a fibre does not reach from one 

 tendinous attachment to the other, but ends with a rounded or tapering extremity,, 

 invested with its sarcolemma, and cohering with neighbouring fibres. Unless when 



