XIII.] THE FROG. 201 



/3. The capillaries, in which the arterial branches 

 end: small vessels forming a close network 

 and frequently branching or anastomosing with- 

 out much altering their size. 



7. The veins, formed by the ultimate union of the 

 capillaries, and increasing in size by union 

 with one another; the blood-flow in them from 

 smaller to larger trunks. 



c. The blood-flow : the current being marked by the 

 solid bodies (corpuscles) carried along in the fluid : 

 it is most rapid in the arteries; slowest, and most 

 constant, in the capillaries. 



3. Place a small drop of water on a bit of a thin cover- 

 glass, and place the bit, with the water downwards, 

 gently on the web : then examine the following points 

 with J or J obj.; note 



a. The walls of arteries, capillaries, and veins. 



a. The arterial walls, tolerably thick, seen as a 

 clear well-defined band on each side of the 

 blood-stream. 



ft. The capillary walls ; difficult to see ; merely a 

 thin somewhat more transparent boundary line. 



7. The venous walls: much like the arterial. 



b. The blood-flow in the small arteries of the web. 



a. The rapid stream in the middle, containing 

 most of the red corpuscles. 



/3. The slower stream along the edge (inert layer), 

 containing many colourless corpuscles. 



c. The flow in the capillaries: much slower than in 

 the arteries; the frequent distortion of the red 



