368 



MANIPULATION. 



some fine cord ; but now, as first practised by Mr. Goadby, the 

 entire body, with the exception of the foot to be examined, is 

 secured in a linen bag, which is fastened to a plate of brass, 

 termed the frog-plate, as shown at a a in fig. 241, and fuUy 



Fig. 241. 



described at page 141 ; this is so contrived as to be held 

 firmly by some part of the stage of the microscope, and 

 moved about with it. Although the shape of the plate, as 

 constructed by our principal instrument-makers, may vary 

 considerably, the mode of using it, nevertheless, is nearly the 

 same in all. A linen bag should be provided, about three or 

 four inches in length, and two-and-a-half inches broad, as 

 shown at 5 6 in fig. 241, having a piece of tape, c c, sewed to 

 each side about midway between the mouth and the bottom, 

 and the mouth itself should be capable of being closed by a 

 drawing string, d d. Into this bag the frog is placed, and 

 only the leg in which the circulation is about to be examined 

 kept out of the mouth, the string, d d, is then to be drawn so 

 tight around the small part of the leg as to prevent the foot 

 from being pulled into the bag, but not to stop the circulation ; 

 three short pieces of thread, /■/_/) are now to be passed round 

 the three principal toes, and the bag with the frog is to be 

 fastened to the plate, a a, by means of the tapes, c c. When 

 this is accomplished, the threads, ///, are to be passed either 

 through some of the holes in the edge of the plate, three of 



