592 



THE MICROSCOPE. 



career. This instrument, made on the model of the 

 Society of Arts Students' Microscope, is well finished, with a 

 coarse and fine adjustment, an adaptation of the , l, and 

 1-inch powers, live-box, and forceps, all packed in a neat 

 case, for the small price of 31. 3s. 



TO VIEW THE CIRCULATION OF BLOOD IN THE FROG. 



The part most commonly employed for this purpose is 

 the transparent web of the hind foot; and in order to 

 secure the animal, and keep its web open, various contri- 

 vances have been had recourse to. The older microsco- 

 pists, Baker, Adams, and others, were in the habit of tying 

 the frog to a frame of brass with some cord; in the 

 present day the entire body of the animal, with the excep- 

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

 silk bag ; and this is fastened to a plate of brass, termed 

 the frog-plate, shown at a a a in fig. 328: this should be 



Fig. 328. 



secured firmly to some part of the stage of the micro- 

 scope, and, at the same time, permit of its being moved 

 about with it. Although the shape of the plate is made 

 to differ by every maker, the mode of using it, neverthe- 

 less, is nearly the same in all. The bag provided should 

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

 half inches broad, as shown at 6 6, having a piece of 

 tape, c c t sewn to each side, about midway between the 



