ARRANGEMENTS FOE DISSECTING 



455 



Dissecting Apparatus. The mode of making a dissection for 

 microscopic purposes must be determined by 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 convenient that the object should 



FIG. 387. Swift's Stephenson binocular dissecting microscope. 



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 dimen- 

 sion 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 one corner into a sort of 

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

 ing. The dark colour of this substance enables it to furnish a back- 



