THE CIRCULATION. 



293 



Placed between the last ramifications of the arteries and the first 

 radicles of the veins, the capillary system is blended with these two 

 orders of vessels without the intervention of any transitional medium. 



Fig. 95. Frog's Web, Highly Magnified. (YEO, after Huxley.) 



A, Wall of capillary. B, Tissue lying between the capillaries. C, Epithelial 

 cells of the skin. D, Nuclei of epithelial cells. E, Pigment-cells, contracted. 

 F, Red blood-corpuscles. O, H, Red corpuscles squeezing their way through a 

 narrow capillary, showing their elasticity. I, White corpuscles. 



The limits assigned to their system by anatomy are purely fictitious. 

 Physiology would be greatly embarrassed if it had to determine the 

 precise point where the vessels are no longer only organs of transport 

 for the blood, but permit an exchange between the blood and tissues 



