354 



MANirULATION. 



coarser dissections will be found in works devoted especially 

 to the subject. 



The dissections in which the microscope is most frequently- 

 employed, are those of the nervous system, either in small 

 animals or in minute parts of the larger ones; for this purpose 

 either of the simple forms, especially that of Messrs. Powell 

 and Lealand, described at page 52, will be found useful. The 

 subject to be dissected may be securely fixed to a loaded cork, 

 and placed in a trough containing water, as shown at c in 

 fig. 234 ; where also are represented, at a h, the two inclined 



Fig. 234. 



supports for the arms, termed rests; these, as described at 

 page 351, consist of two inclined planes of wood, placed one on 

 each side of the trough in which the subject to be dissected 

 is contained, and giving firm support to the arms and wrists 

 of the operator. If the trough be a shallow one, it may be 

 raised on a level with the rests by means of a block, as shown 

 at d. The microscope is to be brought over the trough, and 

 the subject adjusted to the focus, an inch or a two-inch mag- 

 nifier may be employed, or even higher, acccording to the 

 delicacy of the dissection; if the subject be very minute, it 

 may be placed in a small trough and dissected upon the stage 

 of such microscopes as those represented by figs. 36, 37, 38, 

 and 39. These instruments will be found particularly useful 

 in the preparation of muscular and nervous fibres, and objects 

 of a similar kind, previous to their examination under higher 

 powers. The compound microscope, when provided with the 

 erector, described at page 125, will answer very well for many 

 kinds of dissection, as both the object and the dissecting instru- 

 nients are not inverted, but seen in their natural position; 



