ZOOLOGY AND BOTANY, MICEOSCOPY, ETC. 



137 



carried on for hours with perhaps the handle of a dissecting needle, 

 and the ordinary compressors being unsuitable for the purpose, he 

 therefore devised the form shown in fig. 23. 



The plate A is attached to the stage by the catch n and two 

 screws S S. On this plate is a double lever, one arm of which has a 

 movable ring E and adjusting screw St, and the other the knob K. 

 The two levers are so connected with the bent piece C that when K 

 is pressed down the ring E is also pressed towards the stage-plate. 

 Conversely an upward movement of the knob, produced by the spring 

 F, raises the ring again. The screw Si regulates the extent of 

 movement of the end of the lever. 



To use the apparatus the screw St is adjusted so that the ring lies 

 nearly close to the large and thick cover-glass of the preparation, and 

 Si is turned so that the lever can move but very slightly. The object 

 is then focused, and by quick and continuous movement of the knob 

 and the changing pressure on the cover-glass thus produced, tissues 

 (after maceration) can be easily disassociated without danger of being 

 destroyed. The object can also be continually watched with powers 

 up to 600, and all the changes noted. When the cells are isolated 

 they can be seen (by a slower movement of the lever) to move about 

 in all directions, so that they can be observed from all sides. 



If it is desired to press the object, Sj is loosened and St screwed 

 down as far as necessary, and the apparatus can then be used as an 

 ordinary compressor. 



Viguier's Compressorium.* — C. Viguier points out that whilst 

 the compressors in common use enable us to study objects under 

 favourable conditions, which it would be very difficult, if not im- 



FiG. 24. 



possible, to do without them, yet, on the other hand, the objects 

 are almost always destroyed, it being but very exceptionally that a 

 compressed object can be preserved as a permanent preparation, so as 

 to resemble what has been seen in the compressor, and the evil is 



* Arch. Zool. Exper, et Gen., ii. (1884) pp. xii.-xvi. (5 figs.). 



