THE MICROVIVISECTION METHOD. 



ROBERT CHAMBERS, 

 CORNELL UNIVERSITY MEDICAL COLLEGE, NEW YORK CITY. 



The dissection of living cells has hitherto proved inadequate 

 for a study of the physical properties of protoplasm and of its 

 structural components. This is owing largely to a lack of means 

 for the manipulation of dissecting instruments under a sufficiently 

 high magnification of the microscope. 



Before and since Barber first devised his mechanical pipette- 

 holder for the isolation of bacteria, various ingenious methods for 

 the dissection of microscopic objects have been described. They 

 all, however, fall short of Barber's method, because, with them, 

 only comparatively low powers can be used, since the dissecting 

 needles must operate between the objective and the tissue to be 

 dissected. On the other hand, by using needles instead of 

 micro-pipettes, Barber's instrument has been converted into an 

 excellent microdissection apparatus. The needles operate in a 

 shallow hanging drop containing the cells to be dissected which 

 are pressed against the undersurface of a coverslip in a moist 

 chamber. There being no obstacle above the coverslip, oil im- 

 mersion lenses may be used for observation. 



In an article appearing as long ago as 1859, Dr. H. D. Schmidt, 

 of Philadelphia, describes in detail an excellent " microscopic 

 dissector" consisting of a base to be fastened on the stage of a 

 microscope with a number of clamps to hold instruments, each 

 clamp possessing three movements controlled by screws. A 

 lever fastened in one of the clamps holds the tissue in place. 

 Fine scissors, knives or steel needles aqs fastened in the other 

 clamps. By turning the various screws, the instruments can be 

 brought into place and be operated with remarkable accuracy. 

 Dr. Schmidt worked with the tissue, the instruments and the 

 lower lens of the objective immersed in water or diluted alcohol. 

 The full results of his investigations with this instrument were 

 not published until 1869, owing to interruptions due to the Civil 



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