THE STRUCTURE OF THE ELEMENTARY TISSUES. 



83 



fibres themselves are supported in their fasciculus by a scanty amount 

 of areolar tissue containing plasma cells and termed endomysium. 

 Within the areolar tissue supporting the fasciculi and between the fibres 

 are contained the blood-vessels and nerves of the tissue. 



The muscular fibres of each fasciculus are parallel to one another, 

 and generally speaking so are the fasciculi themselves, except that toward 



their terminations they may converge to 

 their insertion into the tendon of the 

 muscle. The fasciculi extend throughout 

 the whole length of the muscle, but they 

 vary in size and in the number of their con- 



Fig. 83. Fig. 84. 



Fig. 83. Transverse section through muscular fibres of human tongue. The muscle-corpuscles 

 are indicated by their deeply-stained nuclei situated at the inside of the sarcolemma. Each muscle- 

 fibre shows "Cohnheim's fields," that is, the sarcous elements in transverse section separated by 

 clear (apparently linear) interstitial substance. X 450. (Klein and Noble Smith.) 



Fig. 84. Muscular fibre torn across; the sarcolemma still connecting the two parts or the fibre. 

 (Todd and Bowman.) 



tained fibres, both in different muscles and also in the same muscle, some 

 muscles having coarse, others fine fasciculi. In some cases it would seem 

 that the perimysium is altogether independent of the external sheath 

 of the muscle. As to the fibres of which the bundles are made up, they 

 have a distinct elastic sheath, the sarcolemma; their size varies consid- 

 erably, their cross-section being from 100,u to 10//, and as regards their 



Fig. 85. Part of a striped muscle-fibre of a water beetle prepared with absolute alcohol. A, 

 Saruoleaiuia; B, Krause's membrane. The sarcolemma shows regular bulgings. Above and below 

 Ivrause's membrane are seen the transparent "lateral discs." The chief mass of a muscular cuin- 

 j.artineut is occupied by the contractile disc composed of sarcous elements. The substance of the 

 individual sarcous elements has collected more at the extremity than in the centre: hence this 



latter is more transparent. The optical effect of this is that the contractile disc appears to ^ 



a "median disc " (Disc of Hensen). Several nuclei of muscle corpuscles, C and D, are shown, and 



in them a minute network, x 300. (Klein and Noble Smith.) 



shape, it is cylindrical or is triangular, quadrilateral, or pentangular with 

 rounded angles. In length the fibres seldom exceed an inch and a half 



