THE ^MUSCULAR SYSTEM 



215 



muscle fibres are formed. In Ihe early stages of their development 

 these are known as myoblasts. The latter develop into muscle 

 fibres in the same manner as described under the histogenesis of 

 muscle (p. 126). 



Blood-vessels. — The larger arteries of muscle run in the perimy- 

 sium, their general direction being parallel to the muscle bundles. 

 From these, small branches are given oft' at right angles. These in 



;^ 



t 



y Sarcoplasm 



Muscle nucleus 

 Transition zone 



Sarcolemma ' 



,'/' 



Tendon fibre bundles 



Tendon nucleus 



Fig. 130. — Junction of Muscle and Tendon showing Continuity of Fibrils and Ex- 

 tension of Sarcolemma beyond the Limits of Cross Striations. Rectus abdominis of 

 frog. X750- (Stohr.) 



turn give rise to an anastomosing capillary network with elongated^ 

 meshes, which surrounds the individual muscle fibres on all sides. 

 From these capillaries, veins arise which follow the arteries. Even 

 the smallest branches of these veins are supplied with valves. 



In tendons blood-vessels are few. They run mainly in the con- 

 nective tissue which surrounds the fibre bundles. Tendon sheaths 

 and bursae, on the other hand, are well supplied with blood-vessels. 



The lymphatics of muscle are not numerous. They accompany 

 the blood-vessels. In tendon definite lymph vessels are found only on 

 the surface. 



