224 



MOUNTING OBJECTS IN FLUID. 



Fig. 102. 



small quantities of fluid required in mounting Microscopic objects, 

 it is essential for the operator to be provided with, the means of 

 transferring very small quantities from the vessel containing it to 

 the slide, as well as of taking up from the slide what may be lying 

 superfluous upon it. Where some one fluid, such as Diluted 

 Alcohol or Goadby's Solution, is in continual use, it will be found 

 very convenient to keep it in a small Bottle of the kind repre- 

 sented in Fig. 102, which is now in general use as a Dropping- 

 bottle. The stopper is perforated, and is elongated below into a 

 fine tube, whilst it expands above into a bulbous funne], the mouth 



of which is covered with a piece of thin 

 Vulcanized India-rubber tied firmly 

 round its lip. If pressure be made on 

 this cover with the point of the finger, 

 and the end of the tube be immersed 

 in the liquid in the bottle, 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 removing the pressure, 

 more fluid will enter. This operation 

 may be repeated 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 the lower end of the tube before the pressure is withdrawn.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 

 Author can speak from large experience of the value of this little 

 implement ; as he can also of the utility of the small Glass Syringe 

 (§ 101) for the same purpose. 



165. There are many Objects of extreme thinness, which 

 require no other provision for mounting them in fluid than an 

 ordinary Glass slide, a Thin Glass cover, and some Gold-size or 

 Asphalte (§ 152). The object having been laid in its place, and a 

 drop of the fluid laid upon it (care being taken that no air-space 

 remains beneath the under side of the object and the surface of 

 the slide), the glass cover is then to be laid upon it, one side being 

 first brought into contact with the slide, and the other held up by 

 a needle-point, and gradually lowered in such a manner that the 

 air shall be all displaced before the fluid. If any air-bubbles 

 remain in the central part of the space between the cover and the 

 slide, the former must be raised again, and more fluid should be 

 introduced ; but if the bubbles be near the edge, a slight pressure 

 on that part of the cover will often suffice to expel them, or the 

 cover may be a little shifted so as to bring them to its margin. 



Dropping Bottle. 



