STKUCTURE OF THE MUSCLES. 



411 



Fig. 264. 



both supports and transmits the vessels and nerves, and also incloses 

 and supports the muscular fibres while in action. The external 

 perimysium contains more elastic tissue than the internal ; and, in 

 estimating its function, it may be regarded as a semi-elastic mem- 

 brane. Liebig found about 5.6 per cent, of the muscle to be con- 

 nective tissue; Von Bibra but 2.2 per cent. There is proportionally 

 more in the calf than in the ox. 



In all muscles, but especially the laxer in structure, a certain 

 number of adipose cells also are found in the areola3 of the peri- 

 mysia ; and these frequently contain beautiful 

 crystals of margaric acid (p. 298). In fat persons 

 these cells are quite abundant among the primi- 

 tive fasciculi even. 



Connections of the Tendons at their Extremities. 



The tendons are connected at one extremity 

 with the belly of the muscle (or the part contain- 

 ing the muscular fibres), and at the other with the 

 bones or other parts moved by the muscles. 



I. The tendons are connected with the muscu- 

 lar fibres in two ways: 1. When the latter lie in 

 the direction of the axis of the muscle, and thus 

 extend through the whole length of the belly of 

 the latter, they pass directly into the fibres of 

 the white fibrous tissue in the tendon, in such a 

 way that there is no sharply defined limit be- 

 tween the two tissues; the tendinous fibre being 

 nearly equal in size to the muscular, and appear- 

 ing to be actually continuous. 1 (Fig. 264.) 2. But 

 when the muscular fibres join the tendons at an 

 acute angle as in the penniform muscles the 

 microscopic conditions are entirely different ; 

 there being an abrupt limit between the two tis- 

 sues. Here the muscular fibres end neatly in an 

 obliquely truncated extremity, with a projecting 

 surface, slightly conoidal, or sometimes per- 

 ceptibly attenuated, and always rounded ; and 



A muscular fibre, (a), 

 from one of the inter- 

 nal intercostal muscles 

 of man, continuous into 

 a tendinous fasciculus 

 (6), into which it passes 

 without any defined li- 

 mitMagnified 350 dia- 

 meters. (KiMiker.) 



1 Dr. Leidy has described a double spiral arrangement of the tendinous fibres 

 around the niyolemma. 



