32 



PSYCHOBIOLOGY 



muscle the nuclei usually lie on the surface of the cell (fiber), flattened be- 

 tween it and the sarcolemma. A few nuclei are found lying inside, among 

 the bundles of fibrils toward the ends of the fibres and especially toward 

 the distal end, at which point elongation in growth takes place. 



In certain red muscle cells, (as in the ocular and respiratory muscles) ; 

 and, in the case of some of the lower vertebrates, in the fibres generally, 

 there are nuclei lying deeper in the cell, embodied among the fibrils, as 

 well as on the surface. 



Connective tissue, including cells with indefinite outlines and flattened 



External perimysium. 



Muscle bundles. 



Internal perimysium. 



Cross section of artery. 

 Muscle spindle. 



Cross section of nerve. 



Muscle of Man. X 60. 



Fig. 21. Cross-section of human striped muscle (omokyoid), magnified 60 diam- 

 eters. (Lewis and Stohr, Histology.) 



nuclei smaller than the nuclei of the muscle fibers, not only surrounds each 

 fiber, but surrounds small bundles of the fibers, bundles of these bundles, 

 and the whole muscle. In cross section this connective tissue forms 

 a continuous network, enveloping and reticulating within the muscle 

 [Fig. 20]. 



The sheath of the whole muscle is the external perimysium, the con- 

 nective tissue within the muscle is the internal perimysium [Fig. 21]. 



