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- 

 tional cases e.g., in the tongue ; here 

 the extremities of the muscle fibres, 

 passing in a transverse direction into 

 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, arid becoming 

 here fixed to a bundle of connective tissue 

 fibrils. The individual fibres have only, 

 as mentioned above, a relatively limited 

 length, so that, following an anatomical 



tru>ed~Mui fascicle from one point of its insertion to 

 the other, we find some muscle fibres 

 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 



cula r Fibres 

 passing into 

 Bundles of 

 Fibrous Tis- 

 sue. 



Termination in 

 Tendon. (Hand- 

 book.) 



