26 THE STRUCTURE OP 



cule, it may be conveyed to the animalcule-cage 

 by means of a glass tube, called a pipette or 

 dipping-tube (fig. 12), which should be dipped into 

 the water where the object is contained, with the fin- 

 ger covered over the upper orifice, so that no air can 

 escape. By taking the finger off when the tube is in 

 the water, the fluid will rush into the tube, and with 

 it the object to be examined. The finger is again 

 applied to the top of the tube, and the fluid ob- 

 tained conveyed to the animalcule cage. Only such 

 a quantity of the water should be allowed to fall 

 out of the tube on to the cage as will enable the 

 observer to put on the cover of the cage without 

 pressing the fluid out at the sides of the cage. If 

 the water is thus allowed to overflow, it runs over 

 the glasses of the cage, and thus obscures vision. 

 An object or objects having been thus placed in the 

 cage, it is conveyed to the stage, and placed in such 

 a position that the ray of light passing from the 

 mirror to the object-glass may pass through it. 

 This having been done, the observer must now 

 place his eye over the eye-piece, and use the screw 

 in the tube, and move the object-glass downwards 

 until he gets a clear view of objects moving in 

 the water. This is called focussing. The glass may 

 then be moved up or down, in order that the best 

 view of the object may be obtained. "When the 

 object-glass is one of high power, the fine adjust* 

 Tnent may be used for this purpose. When the 

 proper focus is obtained, the object may be moved 

 up or down, right or left, with the hand, or by the 

 aid of the screws which are employed in the various 

 forms of what are called inoveahle stages. 



When objects not requiring the live-box or ani- 

 malcule cage are to be observed, they may be 

 transferred to the glass slide by aid of a thin slip 

 of wood, or a porcupine-quill moistened at the end, 



