ELEMENTS OF HISTOLOGY. [Chap. ix. 



and then the increment again changes into muscular 

 substance (Fig. 42). In this way the muscular fibre 

 increases in thickness. Thus one spindle-shaped 

 embryo cell gives rise to one muscular fibre, which, 

 at first very slender, continues to grow in thickness 

 by the active growth of the muscle corpuscles. The 

 sarcolemma appears to be formed from 

 cells other than muscle cells. 



90. The striped muscular fibres, taken 

 as a whole, are, as a rule, spindle-shaped, 

 becoming gradually thinner towards their 

 ends. They are branched in some excep- 

 in the tongue ; here 



tional cases e.g 



the extremities of the 



passing in a transverse 



muscle fibres, 

 direction into 



J 



the mucous membrane, become richly 

 branched. 



91. Muscular fibres terminate in 

 tendons, either by the whole fibre passing 

 into a bundle of connective tissue fibrils 

 (Fig. 43), or by the fibre ending abruptly 

 with a blunt, conical end, ard becoming 

 here fixed to a bundle of connective tissue 

 fibrils. The individual fibres have only, 

 as has been mentioned above, a limited 

 length, so that, following .a fasciculus 

 from one point of its insertion to 

 passing into the other, we find some muscle fibres 

 Fibrous 3 Til terminating, others originating. This 

 takes place in the following way : the 

 contents of a fibre suddenly terminate, 

 while the sarcolemma, as a fine thread, 



becomes interwoven with the fine connective tissue 



between the muscular fibres. 



92. The striped muscular fibres of the heart 



(auricles and ventricles) and of the cardiac ends of 



the large veins (the pulmonary veins included) differ 



Fig. 43. Two 

 Striped Mus- 

 cular Fibres 

 ssing into 

 undles of 

 ibrous Tis- 



Tennination in 

 Tendon. (Hand- 

 book.) 



