PATTERNS OF THE A-V PATHWAYS 90 1 



-Ut 



fig. 5. Vascular pattern of the hamster cheek pouch. 

 (Courtesy of Dr. E. P. Fowler, Jr.) 



degree in the last eight decades. The early information 

 comes from studies of injected and fixed material, and 

 in recent years there have been investigations using 

 microscopic techniques on living animals. 



Krogh (73) reviews the work of Spalteholz (116), 

 who depicted the vascular arrangement as follows: 

 freely branching arteries with numerous anastomoses 

 between the branches form a primary network which 

 in turn gives off anastomosing small arteries that form 

 a second network. Arterioles branch from this net- 

 work, usually at right angles to muscle fibers at 

 regular intervals. The arterioles then split up into a 

 large number of capillaries which run along parallel 

 to the muscle fibers with numerous anastomoses. The 

 capillaries unite into venules. The pattern of the 

 venous system is almost exactly that of the arterial 

 systems. 



Clark (37) and Walls (126) state that skeletal 

 muscle, which is highly vascular, is supplied by 

 branches from neighboring arteries which invade the 

 epimysium and travel into the perimysium, dividing 



fig. 6. Vascular network of hamster cheek pouch near 

 buccal end, lead chromate injection. [From Poor (97).] 



as they do so. Various branches of the vessels entering 

 the perimysium anastomose with one another. The 

 finer branches lie transversely to the long axes of the 

 muscle fibers and give rise to the capillaries which run 

 parallel to the muscle fibers. These parallel capil- 

 laries lie in the endomysium. This, then, is the anatom- 

 ical sequence: arteries and veins run together until 

 terminal arterioles and venules are reached. The 

 terminal arterioles and venules then come ofF of the 

 parent vessels in alternate sequence. The capillaries, 

 running longitudinally between muscle fibers, are 

 connected frequently by transverse vessels which run 

 over or under the intervening fibers and thus form a 

 fine capillary network of tiny oblong meshes. 



Zweifach & Metz (151, 152) have studied the 

 vascular supply of the spinotrapezius muscle in the 

 rat. Their observations were primarily of vessels in the 

 epimysium and the perimysium. They found two 

 distinct components in the capillary circulation of 

 muscle bundles, /) a vascular bed that was distributed 

 along the natural cleavage planes in the connective 

 tissue sheath that binds collections of muscle bundles 

 together, and 2) a second capillary network originated 

 by short muscular arterioles which penetrate into the 



