96 



THE FROG 



CHAP. 



the capillary network, and will be able to trace the 



blood from an artery, through the capillaries, into a vein. 



The same thing can be seen in other transparent 



FIG. 24. Blood-vessels of the web of a Frog's foot seen under a low magnifying power. 



a. small arteries ; v. small veins. The minute tubes joining the arteries to the 



veins are the capillaries. The arrows show the direction of the circulation. 



In the small portion marked off, the pigment cells of the skin, which occur 



throughout the web, are also represented. (From Huxley's Physiology.) 



organs ; and by injecting the vascular system with a 

 fluid injection-mass, such as gelatine suitably coloured, 

 it can be proved that all parts of the body are permeated 

 with a capillary network into which the blood is passed 



