142 THE MICROSCOPE AND ITS REVELATIONS. 



therefore in a line with the axis of the body. If the object be not- 

 'mounted,' and be of such a kind that it is best seen dry, it may be sim- 

 ply laid upon the glass Stage-plate ( 120), the ledge of which will pre- 

 vent it from slipping off when the Microscope is inclined; and a plate 

 of thin glass may be laid over it for its protection, if its delicacy should 

 seem to render this desirable. If, again, it be disposed to curl up, SO' 

 that a slight pressure is needed to flatten or extend it, recourse may be had 

 to the use of the Aquatic Box ( 122) or the Compressor ( 125), without the 

 introduction of any liquid between the surfaces of glass. In a very large 

 proportion of cases, however, either the objects to be examined are al- 

 ready floating in fluid or it is preferable, to examine them in fluid, on 

 account of the greater distinctness with which they may be seen. If such 

 objects be minute, and the quantity of liquid be small, the drop is sim- 

 ply to be laid on a slip of glass, and covered with a plate of thin glass; if 

 the object or the quantity of liquid be larger, it will be better to place it. 

 in a concave slide or cell; whilst, if the object have dimensions which 

 render even this inconvenient, the Zoophyte Trough ( 124) will afford 

 the best means for its examination. In the case of minute living ani- 

 mals, whose movements it is desired limit (so as to keep them within the 

 field of view) without restraining them by compression, the Author has 

 found the following plan extremely convenient. The drop of water 

 taken up with the animal by the Dipping-tube being allowed to fall into 

 a concave slide (Fig. 122), the whole of the superfluous water may be re- 

 moved by the Syringe ( 127), only just as much being left as will keep 

 the animal alive. If the animal be very minute, it is convenient to effect 

 this withdrawal by placing the slide on the stage of the Dissecting Mi- 

 croscope ( 44), and working the Syringe under the magnifier; and it will 

 be found after a little practice, that the complete command which the 

 operator has over the movements of the piston, as well as over the place 

 of the point of the syringe, enables him to remove every drop of super- 

 fluous water without drawing the animal into the syringe. When, on 

 the other hand, it is desired to isolate a particular animal from a number 

 of others, the syringe may be conveniently used, after the same fashion, 

 to draw it up and transfer it to another slide; care being, of course, 

 taken that the syringe so employed has a sufficient aperture to receive it 

 freely. If it be wished to have recourse to compression, for the expansion 

 or flattening of the object, this may be made upon the ordinary slide, by 

 pressing down the thin-glass cover with a pointed stick; and this method 

 which allow the pressure to be applied at the spot where it is most re- 

 quired, will generally be found preferable for delicate portions of tis- 

 sue which are easily spread out, and which, in fact, require little other 

 compression than is afforded by the weight of the glass cover, and by the 

 capillary attraction which draws it into proximity with the slide beneath. 

 A firmer and more enduring pressure may be exerted by the dexterous 

 management of a well-constructed Aquatic Box; and this method is pecu- 

 liarly valuable for confining the movements of minute animals, so as to 

 keep them at rest under the field of the microscope, -without killing 

 them. It is where a firm but graduated pressure is required, for the 

 flattening-out of the bodies of thin semi-transparent animals, without 

 the necessity of removing them from the field of the Microscope, that 

 the Compressor is most useful. 



142. In whatever way the Object is submitted to examination, it must, 

 be first brought approximately into position, and supported there, just 

 as if it were in a mounted Slide. The precise mode of effecting this will 



