20 



Use of Ordinary Binocular fob Dissecting. 

 By John Tatham, M.A., M.D. 



{Read December 20, 1895.) 



For many years past I have been trying to hit upon some 

 simple method of using the stereoscopic binocular instrument for 

 purposes of dissection, and of mounting slides for the microscope, 

 because I have repeatedly found that the use of the best simple 

 microscope for long periods does seriously impair the sensitive- 

 ness of the retina for observation with the compound instrument. 



I have brought with me the stand which I now employ. It 

 is a very small binocular, on the Rousselet model, and is fitted 

 with a rack-work substage. Into this substage is fitted a brass 

 ring carrying a plate, or supplementary stage, of the form now 

 shown. This supplementary stage is made of exactly the same 

 width as the principal stage of the microscope, and the sliding 

 object carrier of the latter is made to slide easily over the supple- 

 mentary stage. The object of this arrangement will be shown 

 hereafter. When used for dissecting or mounting, the instru- 

 ment is placed in the vertical position, on a table only so high 

 as is necessary to allow of work in a sitting posture. A low 

 power, say an inch, two inch or three inch, is screwed into the 

 nose-piece. The objective is then racked down through the 

 aperture of the principal stage, and is focussed on the object 

 lying on the supplementary stage already described, a bulls- 

 eye condenser, of the aplanatic form suggested by Mr. Nelson, 

 being used in the case of opaque objects. 



Two wedges, or inclined planes of wood, are arranged as 

 supports for the wrists, one on either side the microscope, or in 

 default of these a couple of thick books can be similarly used. 



It only remains to be said that with the above simple arrange- 

 ment, which certainly is not an expensive one, any small 

 binocular can readily be converted into a dissecting microscope, 

 or a mounting instrument, or it can be used with a four-inch or 

 lower power, for the examination of animal or vegetable forms 



