392 



ZOOLOGY. 



[Sect, XI. 



-paper), wonderfully minute objects can be dis- 

 sected ; needles bent at their tips are convenient for 

 some purposes. Arm supports are useful in minute dis- 

 sections; two blocks of wood with inclined surfaces, 

 coming up a little below the level of the stage, and 

 resting partly on the stand of the microscope, can be 

 mr-^e by a common carpenter. As it is often rather 

 dark in the cabins of ships, a large bull's-eye glass on a 

 stand (such as arc sold with most compound microscopes) 

 would be most useful to condense the light from a lamp 

 on an opaque object, or to increase it when transmitted. 

 Besides the needles, fine pointed forceps, pointed scissors, 

 and eye scalpels are requisite, Tlie French use an 

 instrument called a microtome, and consider it most 

 useful : others prefer finely pointed scissors, with one 

 leg long and thick, to be held like a pen, and the other 

 quite short, to be pressed by the fore- finger, and kept 

 open by a spring. A live-box to act as a compressor, or 

 still better a proper compressor closed by a screw, and 

 both made to drop into the rim of the stage, are valuable 



aids for making out the structure of transparent animals 



or organs. The observer should be provided with three 

 slips of glass, or still better with three circular plates, made 

 to drop into the stage of his microscope, and graduated 

 into tenths, hundredths, and thousandths of an inch, to 

 =erve as micrometers, on which to place and measure any 



fc^ 



object 



le is examining. Some watch-glasses are very 

 as temporary receptacles for small sea-animals. 

 Minute parts after dissection can be preserved for years 



useful 



m 





vy vjcak spirits of wine 



placed on slips of mass 



D 



by covering them, when 

 by ^mall portions of very thin 



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