58 THE MICROSCOPE. 



should not be so far advanced as to have lost its early 

 transparence of skin ; and it is further essential to the 

 tracing out the course of the abdominal vessels, that 

 the creature should be kept without food for some 

 days, so that the intestine may empty itself. This 

 starving process reduces the quantity of red corpuscles, 

 and thus renders the blood paler ; but this, although 

 it makes the smaller branches less obvious, brings the 

 circulation in the larger trunks into more distinct 

 view." The circulation of blood in a young tadpole 

 is a most astonishing spectacle. The plate will serve 

 to give you some slight notion of the internal organs ; 

 by-and-by, when you become more experienced, you 

 should read Mr. Whitney's remarks on that subject 

 in Vol. X. of the Transactions of the Microscopical 

 Society, 1862. If you desire to study the circulation 

 of blood in a frog's foot, you should select a young 

 specimen with a thin web. But how are you to keep 

 the frog quiet under inspection ? Microscope-makers 

 sell an especial apparatus for this purpose, called a frog- 

 plate ; but you can easily cut out a wooden imitation, 

 which will serve your purpose completely. Provide 

 yourself with a piece of thin wood or cork, about nine 

 inches long and three inches wide; towards the middle 

 of its length cut a hole about half an inch in diameter. 

 Wrap the whole of the frog, except one leg, in a piece 

 of wet calico, and fasten him, but not too tightly, on 

 the cork-plate ; spread out the exposed foot over the 

 aperture, and by means of a few small pins fasten the 

 foot to the cork. Then put the cork-plate upon the 

 stage of the microscope, and secure it by means of 

 tape. Moisten the frog's web with a spot of water, 

 and examine it under the microscope with a power of 

 about 100 diameters, and you will see a wonderful 

 sight. Torrents of blood flow with great rapidity, 

 crossing and re-crossing each other ; sometimes there 



