682 



THE MICROSCOPE. 



or wing of tlie Long-eared Bat, as Professor Wharton Jones 

 pointed out. 



To view the circulation of blood in the I'rog's foot, the 

 older microscopists, Baker, Adams, and others, were in the 

 habit of tying the frog to a frame of brass ; at the present 

 time the entire body of the animal, with the exception 

 of the foot about to be examined, is secured in a black 

 silk bag, and this is fastened to a plate, termed the frog- 

 plate, shown at a a a in fig. 31 G. The bag provided should 



Fi''. 316. 



be from three to four inches in length, and two and a half 

 inches broad, shown at h b, having a piece of tape, c c, 

 sewn to each side, about midway between the mouth and 

 the bottom ; and the mouth itself capable of being closed 

 by a drawing-in string, d d. Into this bag the frog is 

 placed, and only the leg which is about to be examined 

 kept outside ; the string d d must then be drawn suf- 

 ficiently tight around the small part of the leg to prevent 

 the foot from being pulled into the bag, but not to stop 

 the circulation ; three short pieces of thread, ///, are now 

 passed around the three principal toes; and the bag with 

 the frog must be fastened to the plate a a by means of the 

 tapes c c. AVlien this is accomplished, the threads /// 

 are passed either through some of the holes in the edge 

 of the plate, three of which are shown at g g g, in order 

 to keep the web open ; or, what answers better, in a series 



