BLOOD 43 



ing instrument to look through it at living structures, and 

 watch the different processes of life as they are carried on 

 under our eyes. Nor 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 

 microscopically 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 transparency. 



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 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 without 

 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 mar- 

 gins, 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 comfortable as 

 circumstances will admit. 



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

 proceed to wrap up our unconscious subject. When we 



