536 



Comparative Animal Physiology 



TABLE 66 (continued) 



BLOOD VOLUME IN MILLILITERS OF BLOOD PER 



100 GRAMS OF BODY WEIGHT 



built up by the heart, and the volume of blood. Peripheral resistance is 

 varied by constriction and dilatation of arterioles and capillaries, constriction 

 of arterioles being by action of smooth muscle and constriction of capillaries 

 largely by endothelial contraction. ^-•*' ^^"^ ^- The peripheral responses may 

 be local, as by direct irritation of capillaries or by axon reflexes (i.e., reflexes 

 involving efferent branches of sensory neurones), or the peripheral responses 

 may be truly reflex, or hormonal. Receptors are located in the carotid sinus, 



