204 BLOOD 



bell shape, etc.). These are believed by some (Weidenreich, Lewis, Mi- 

 not, and others) to be the more normal in shape; however, there remains 



FIG. 217. OXALATED PLASMA OF HUMAN BLOOD CLOTTED WITH THROMBIN, 

 SHOWING FIBRIN NEEDLES. X 512. 



(After Howell, Amer. Jour. PhysioL, 35, 1, 1914.) 



little doubt that the circular biconcave disk shape is the normal (origi- 

 nal), the saucer or cup shapes, the derived forms, the result of modifi- 



