THE CAPILLARIES 



151 



Nerves. Most of the arteries are surrounded by a plexus of nerves or 

 nerve fibers, which twine around the vessel. The smaller arteries also have 

 a delicate network of similar nerve fibers many of which appear to end near 

 the nuclei of the transverse muscular fibers. 



The Capillaries. In all vascular textures, except some parts of 

 the corpora cavernosa of the penis, of the uterine placenta, and of the spleen, 



FIG. 149. Capillaries of Striated Muscular Tissue. From a cat. Magnified 300 diameters. 

 (Heitzmann.) A, Artery; V, vein. 



the transmission of the blood from the minute branches of the arteries to the 

 minute veins is effected through a network of capillaries. They may be 

 seen in all minutely injected preparations. 



The point at which the arteries terminate and the capillaries commence 

 cannot be exactly defined, for the transition is gradual. The capillaries 

 maintain essentially the same diameter throughout. The meshes of the 

 network that they compose are more uniform in shape and size than those 

 formed by the anastomoses of the minute arteries and veins. 



