212 THE MICROSCOPE AND ITS REVELATIONS. 



this will rise into it on the removal of the finger; if, then, the funnel be 

 inverted, and the pressure be re-applied, some of the residual air will be 

 forced out, so that by again immersing the end of the tube, and remov- 

 ing the pressure, more fluid will enter. This operation may be repeat- 

 ed as often as may be necessary, until the bulb is entirely filled; and 

 when it is thus charged with fluid, as much or as little as may be needed 

 is then readily expelled from it by the pressure of the finger on the cover, 

 the bulb being always refilled if care be taken to immerse the lower end 

 of the tube before the pressure is withdrawn. The 

 FIG. 138, Author can speak from large experience of the value 



" of this little implement; as lie can also of the utility 

 of the small Glass Syringe ( 127) for the same pur- 

 pose, and this not only for fine Aqueous liquids, but 

 also for Glycerine jelly, and Canada balsam. For 

 these media having been poured, when liquefied by 

 warmth, each into its own syringe (its piston having 

 been previously drawn out), can be forced out as oc- 

 casion requires, by pressure on the replaced piston, 

 which may be graduated with great nicety, when the 

 syringe has been gently warmed by lying for a short 

 Dropping-Bottie. ^ me on * ne Water-bath cover ( 177). Farrants's 

 medium may be conveniently used in the same manner. 

 But the solutions of Canada Balsam and Gum Dammar in volatile fluids 

 will not be sufficiently secure from change by evaporation through the 

 point of the syringe; and are better kept in wide-mouthed capped jars, the 

 liquid being taken-out on a pointed glass rod, or ( stirrer ' cut to such a 

 length as will enable it to stand in the jar when its cap is in place. Great 

 care should be taken to keep the inside of the cap and the part of 

 the neck of the jar on which it fits, quite clean, so as to prevent the fix- 

 ation of the neck by the adhesion between these two surfaces. Should 

 such adhesion take place, the cautious application of the heat of a spirit- 

 lamp will usually make the cap removable. In taking out the liquid, 

 care should be taken not to drop it prematurely from the rod, a mis- 

 chance which may be avoided by not taking up more than it will properly 

 carry, and by holding it in a horizontal position, after drawing it out of 

 of the bottle, until its point is just over the slip or cover on which the 

 liquid is to be deposited. 



208. Mounting Thin Sections. The thin sections cut by the Micro- 

 tome, or membranes obtained by Dissection, do not require to be placed 

 in cells when mounted in any viscid medium; since its tenacity will serve 

 to keep off injurious pressure by the cover-glass. "When the preparation 

 has been previously immersed in Aqueous liquids, and is to be mounted in 

 glycerine, glycerine jelly, or Farrants's medium, the best mode of placing 

 it on the slide is to float it in a saucer or shallow capsule of water, to place 

 the slide beneath it, and, when the object lies in a suitable position above 

 it, to raise the slide cautiously, holding the object in place by a needle, 

 until it is entirely out of water. The slide is then to be wiped by an 

 absorbent cloth, taking care not to touch the object with it; and the 

 small quantity of liquid still surrounding the object is to be carefully 

 drawn off by a bit of blotting-paper, care being taken not to touch the 

 object with it (as its fibres are apt to adhere), or to leave any loose fibres 

 on the side. Before the object is covered, it should be looked at under a 

 Dissecting or Mounting Microscope, for the purpose of improving (if 

 desirable) its disposition on the slide, and of removing any foreign particles 



