30 EVENINGS AT THE MICROSCOPE. 



tissues, which are then clothed on both surfaces with the 

 common skin. But you ask how we can induce the Frog 

 to be so polite as to hold his paw up and keep it steady 

 for our scientific investigation. We will manage that with- 

 out difficulty. 



Most microscopes are furnished (among their accessory 

 apparatus) with what is called a frog-plate, provided for 

 this very demonstration. Here is mine. It is a thin 

 plate of brass, two inches and a half broad and seven long, 

 with a number of small holes pierced through it along 

 the margins, and a large orifice near one end, which is 

 covered with a plate of glass. This is to be Froggy's bed 

 during the operation, for we must make him as comfort- 

 able as circumstances will admit. 



Well, then, we take this strip of linen, damp it, and 

 proceed -to wrap up our unconscious subject. When we 

 have passed two or three folds round him, we bind a tape 

 round the whole, with just sufficient tightness to keep him 

 from struggling. One hind-leg must project from the 

 linen, and we now pass a needle of thread twice or thrice 

 through the drapery and round the small of this free leg, 

 so as to prevent him from retracting it. 



Here then he lies, swathed like a mummy, with one 

 little cold foot protruded. Lay him carefully on the brass 

 plate, so that the webbed toes shall stretch across the 

 glass. Now, then, we pass another tape through the mar- 

 ginal holes, and over the body, to bind it to the brass ; of 

 course taking care not to cut the animal, but only using 

 just as much force as is needful to prevent his wrigglings. 

 Now a bit of thread round each toe, with which we tie it 

 to as many of the holes, so as to expand the web across 

 the glass. A drop of cold water now upon the swathes to 

 keep him cool, and a touch of the same with a feather 

 upon the toes to prevent them from drying (which must 

 be repeated at intervals during the examination) and he 

 is ready. 



