THE MUSCULAR TISSUES. ,. 



or the fineness, macroscopically appreciable, of the muscle largely 

 depends. The entire muscle is invested in a fibrous sheath, the 

 epimysium, derived from the denser layers of the interfascicular 

 connective tissue. 



When contraction takes place, the entire muscle becomes shorter 

 and, at the same time, broader ; the striae also 

 participate in the changes, becoming narrower. 

 These phenomena, however, affect only a 

 limited part of the fibre at one time, consecu- 

 tive portions being influenced in regular se- 

 quence, so that the changes pass along the 

 fibre as a contraction wave ; after the passage 

 of the wave the muscle resumes its previous 

 condition. 



In short muscles the individual fibres quite 

 frequently extend the entire length ; in long 

 ones, on the contrary, the fibres are shorter 

 than the muscle, being generally some 30-45 

 mm. long; sometimes, however, the fibres 

 reach a length of 120 mm. by 10-50 mm. in 

 width (Felix). The fibres, as a whole, are gen- 

 erally somewhat spindle-shaped, being slightly larger in the middle ; 

 the ends of the fibres are more or less pointed, although blunted 



or club-shaped, and, more rarely, 



FIG. 76. branched, extremities are not un- 



common. Branched and anas- 

 tomosing fibres frequently occur 

 (Gage), especially in the tongue 



FIG. 77. 



Muscle-fibres in transverse 

 section, highly magnified : A , 

 portion of human muscle : the 

 small, irregular areas are the 

 fields of Cohnheim (c) ; B, 

 semi-diagrammatic view show- 

 ing the groups of muscle col- 

 umns composing Cohnheim's 

 fields ; , nucleus ; m, groups 

 of muscle-columns. 



Voluntary muscle in transverse section : the 

 irregular polyhedral areas (/) are the individual 

 muscle-fibres in section, held together by the en- 

 domysium (e) ; the primary bundles of the fibres 

 are enclosed by the denser perimysium (/). 



Branched voluntary-muscle fibres from the 

 tongue. 



and ocular muscles. When the individual fibres do not extend the 

 length of the entire muscle, the sarcous substance terminates in 



5 



