ii2 EVENIKGS AT THE MICROSCOPE. 



they i^ossess during tlie life of their o^vllers. It is. 

 indeed, one of the most instructive modes of using tliis 

 wonder-worldng instrument to look through it at liv- 

 ing structures, and watch the different processes of life 

 as they are carried on under our eyes. Xor is this at 

 all difficult to accomplish ; for a large number of 

 animals are so small that we can easily put them upon 

 the stage of the microscope, and withal so transparent 

 that their integuments and various tissues offer little 

 or no impediment to our discerning the forms and 

 movements of the contained viscera. And in cases 

 where the entire animal is too large to be viewed mi- 

 croscopically as a whole, it sometimes happens that, by 

 a little contrivance, we can so secure the creature as 

 to look, without interruption, on certain parts of the 

 body which afford the requisite minuteness and trans- 

 parency. 



I have here a living Frog. You perceive that the 

 web which connects the toes is exceedingly thin and 

 translucent, yet arteries and veins meander through its 

 delicate tissues, which are then clothed on both surfaces 

 with the common skin. But you ask how we can in- 

 duce the Frog to be so polite as to hold his paw up and 

 keep it steady for our scientific investigation. We will 

 manage that without difficulty. 



Most microscopes are furnished (among their acces- 

 sory apparatus) witli what is called a frog-plate, i3ro- 

 vided 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. Tliis 

 is to be Froggy's bed dui-ing the operation, for we 



