4/6 PREPARATION, MOUNTING, AND COLLECTION OF OBJECTS 



Mounting. By the term ' mounting ' is meant the arranging of 

 specimens on slides in such media and in such a manner as are most 

 favourable for the demonstration of their minute structure by the 

 microscope. In the case of the most numerous and important class 

 of objects that it is the function of the microscope to scrutinise, 

 namely, those derived from the substance of animal or vegetable 

 organisms, it is found that no methods of mounting will avail to re- 

 veal their minute structure unless the specimens have first been 

 submitted to the frequently very elaborate processes of previous 

 preparation to be hereafter described under the heads of Fixing, 

 Imbedding, Section-cutting, titainmy, and the like. But still there 

 are many objects of interest and beauty that can be satisfactorily 

 mounted without the aid of these elaborate processes of previous 

 preparation. And as also the manipulations of mounting sensu 

 stricto are in principle the same in both cases, it appeal's advisable 

 to make the description of the processes of mounting precede that 

 of the processes of previous preparation ; merely warning the 

 beginner that in the case of the majority of specimens intended to 

 illustrate the minute structure of the tissues of either animals or 

 plants, such previous preparation is a sine qua non. 



The manipulations of mounting will alone be described here, the 

 most useful mounting media being described later on (' Preserva- 

 tive and Mounting Media '). 



In dealing with the small quantities of fluid media required in 

 mounting microscopic objects, it is essential for the operator to be 

 provided with the means of transferring very small quantities from 

 the vessels containing them 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 glycerin, is in continual use, it will be found very con- 

 venient to keep it in the small dropping-bottle represented in fig. 403. 

 The stopper is perforated, and is elongated below into a fine tube, 

 whilst it expands above into a bulbous funnel, the mouth of which is 

 covered with a piece of thin vulcanised indiarubber 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 reapplied, 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 uith 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 bull) being always 

 refilled if care be taken to immerse the lower end of the tube before 

 the pressure is withdrawn. We speak from large experience of the 

 \alue of this little implement, which is very clean, simple, and use- 

 ful. Bat the small pipettes now used so commonly for filliny the 

 stylographie pens, fitted into the centre of a cork and placed in any 

 wide-mouthed bottle, \\ill lie found to be. though less elegant, 

 equally useful and much less costly. 



Solutions of Canada balsam and yum-dammar in volatile fluids 



