MUSCULAR TISSUE. 



the other hand it may be cleft at one end into two cr three portions, in 

 which case it is named bicipital or tricipital. 



Fig. LIX. Fig. LX. 



Fig. LTX. A, SMALL PORTION OP MUSCLE, NATURAL SIZE ; B, THE SAME MAGNIFIED 

 5 DIAMETERS, CONSISTING OF LARGER AND SMALLER FASCICULI, SEEN IN A TRANSVERSE 

 SECTION. 



Fig. LX. A FEW MUSCULAR FIBRES, BEING PART OP A SMALL FASCICULUS, HIGHLY 



MAGNIFIED, SHOWING THE TRANSVERSE SlRI^!. 



a, end view of b, b, fibres ; c, a fibre split into its fibrils. 



The muscular fibres are collected into packets or bundles, of greater or 

 less thickness, named fasciculi or lacerti (fig. LIX.), and the fibres themselves 

 consist of much finer threads, visible by the aid of the microscope, which 

 are termed muscular filaments, fibrillse or fibrils (fig LX., c). The fibrils 

 run parallel with each other in the fibres, and the fibres are parallel in the 

 fasciculi ; and the fasciculi extend continuously from one terminal tendon to 

 the other, unless in those instances, like the rectus muscle of the abdomen 

 and the digastric of the inferior maxilla, in which the fleshy part is inter- 

 rupted by interposed tendinous tissue. The fasciculi also very generally 

 run parallel, and, although in many instances they converge towards their 

 tendinous attachment with various degrees of inclination, yet in the volun- 

 tary muscles they do not interlace with one another. 



Shtath. An outward investment or sheath of areolar tissue (sometimes 

 named perimysium) surrounds the entire muscle, and sends partitions in- 

 wards between the fasciculi ; furnishing to each of them a special sheath. 

 The areolar tissue extends also between the fibres, but does not afford to 

 each a continuous investment, and therefore cannot be said to form sheaths 

 for them. Every fibre, it is true, has a tubular sheath ; but this, as will 

 be afterwards explained, is not derived from the areolar tissue. The tissue 

 of the sheath is composed of elastic (yellow) as well as of white fibres ; but 

 the elastic element is found principally in its investing (as distinguished 

 from its penetrating) portion. The chief uses of the areolar tissue are to 

 connect the fibres and fasciculi together, and to conduct and support the 

 bloodvessels and nerves in their ramifications between these parts. The 

 relation of these different subdivisions of a muscle to each other, as well 

 as the shape of the fasciculi and fibres, is well shown by a transverse 

 section (figs. LIX. and LX.). 



