ZOOLOGY AND BOTANY, MICROSCOPY, ETC. 



863 



in which the pressure is effected by the action of a screw on an inclined 

 plane A, and working against the spring K. When the screw is 

 turned on one side, the upper part of the compressor can be raised 

 on the pivots BB' as shown in fig. 177. The frame holding the upper 

 plate has a gimbal motion on the pivot D (and the corresponding 

 one on the opposite side) and the frame can be detached by pressing 

 the pin C and the corresponding one on the opposite side, causing 

 the frame-holder to spring open slightly. The two glasses being 

 oblong and lying crossed it is easy to add a drop of liquid during 

 compression. 



The compressor can be reversed, and in that case rests on the 

 three small pillars which are high enough to allow the milled head 

 of the screw to clear the stage.* 



Coles' Self-adjusting Frog-plate.f — Mr. A. H. Coles' frog-plate is 

 shown in fig. 179 (under side). It is 2 in. by 5 in., and it is claimed 

 that " its adjustability, lightness, simplicity, the ease with which the 



Fig. 179. 



frog is secured without injurious pressure or loss of any blood, together 

 with its cost, commend it to all users of the Microscope." 



The binding cord is passed as usual over the plate and round the 

 pins, and its free end is secured by simply drawing it under one of 

 the small spring clips on the edge of the plate. The long springs 

 are for holding the plate securely on any stage. 



Micro-stroboscope for observing Muscle-contraction in Insects.J 

 Prof. E. v. Fleischl employed in his experiments on muscle con- 

 traction in insects a " micro-stroboscope." 



The poles of a small chromic acid battery were connected with 

 the extremity of the exposed nerve proceeding from the insect wing, 

 and the electric connection was made through the intermediation of 

 small strips of tinfoil, insulation being effected by vaselin. This 

 was carried out on the stage of a Microscope, and the observations were 

 made under comparatively low powers. As the images of the tetan- 

 ized muscle were imperfect and distorted, a " stroboscopic " disc of 



* See Arch, de Zool., 1886. 



t Micr. Bull. (Queen's) iii. (1886) p. 11 (1 fig.). 



% Arch. f. Anat. u. Physiol., 1886 (Physiol. Abtheil.) pp. 67-71. 



