EXPLANATION OF THE PLATES. 



PLATE VI. 



Fig. 1. Is a more highly magnified representation of the cir- 

 culation in the capillaries of the web of the foot of 

 the frog ; in it the white and red corpuscles as well 

 as the epidermis are more clearly defined, two of the 

 white corpuscles are seen to be of an oval form, re- 

 sulting from compression between the red blood 

 discs and the walls of the vessels. This figure is 

 magnified 670 diameters. 



2. Exhibits a portion of a larger vessel also taken from 

 the web of the foot of the frog, in it the white cor- 

 puscles are seen to have collected in considerable 

 quantity, as they are frequently observed to do after 

 long exposure of the web to the action of the air ; 

 two cells or globules of a very peculiar structure 

 are likewise figured, these open on the surface and 

 possibly are mucous crypts. This representation 

 is magnified 900 diameters. 



