XVIl] BLOOD VESSELS. CIRCULATION 139 



the capillaries, their outline is lost. (For other changes 

 in inflammation cp. 9.) 



d. The effects are local, they are not seen in the 

 other web. 



e. If .the injury to the vessels has been slight, the 

 circulation may be seen to be re-established in the 

 stagnated spots, the corpuscles gradually recover their 

 outline and are carried off by the current ; this is not 

 seen if stasis has set in, i.e. if the blood has clotted. 



8. Observe now the circulation in the tongue ; 

 the frog being on its belly, draw forward the tongue 

 over the hole in the stage and pin out the two 

 cornua ; the tongue at first pale soon becomes flushed 

 and its vessels full of blood. With a low power the 

 peripheral zone in the arteries and veins will probably 

 be seen better than in the web. 



9. Replace the tongue. On the right side make 

 a cut through the skin and body wall, 1 J to 2 cm. long, 

 midway between the dorsal and ventral surfaces and 

 rather nearer the hind than the fore limbs. Place the 

 frog against the hole in the side of the frog-board, and 

 pull out the coil of the intestine above the rectum, pin 

 it out with hedgehog quills, cut the quills off short, 

 and put small pads of blotting-paper wet with salt 

 solution round the edge of the intestine, cover with a 

 piece of cover-slip, and observe the circulation in the 

 mesentery. 



The exposure will probably cause some degree of 



