CHAPTER V. 



PREPARATION, MOUNTING, AND COLLECTION OF OBJECTS. 



UNDER this head it is intended to give such general directions 

 respecting the preparation, mounting, and collection of Objects, 

 as will supersede the necessity of frequent repetition when each 

 particular class is described ; and also to enumerate the materials 

 and appliances, which will be required or found advantageous. 



SECTION 1. PREPARATION OF OBJECTS. 



104. Microscopic Dissection. The separation of the different 

 parts of an Animal or Vegetable structure by dissection, so as 

 to prepare any portion for being minutely examined under the 

 Microscope should be accomplished, so far as may be found 

 practicable, with the naked eye ; but the best mode of doing 

 this, will depend in great degree upon the size and character 

 of the object. Generally speaking, it will be found advantageous 

 to carry on the dissection under water, with which alcohol should 

 be mingled where the substance has been long immersed in 

 spirit. The size and depth of the vessel should be proportioned 

 to the dimensions of the object to be dissected ; since, for the 

 ready access of the hands and dissecting instruments, it is con- 

 venient that the object should neither be far from its walls, nor 

 lie under any great depth of water. Where there is no occasion 

 that the bottom of the vessel should be transparent, no kind of 

 dissecting-trough is more convenient, than that which every one 

 may readily make for himself, of any dimensions he may desire, 

 by taking a piece of sheet gutta percha of adequate size and 

 stoutness, warming it sufficiently to render it flexible, and then 

 turning up its four sides, drawing out each corner into a sort of 

 spout, which serves to pour away its contents when it needs 

 emptying. The dark color of this substance enables it to furnish 

 a background, which assists the observer in distinguishing deli- 

 cate membranes, fibres, &c., especially when magnifying lenses 

 are employed ; and it is hard enough, without being too hard, 

 to allow of pins being fixed into it, both for securing the object, 

 and for keeping apart such portions as it is useful to put on the 

 stretch. When glass or earthenware troughs are employed, a 

 piece of sheet-cork, loaded with lead, must be provided, to an- 



