MEMORANDA. 273 



On a new Reagent for the Exhibition of the Axis-Cylinders in 

 Nerves.— I believe the fact I am about to state worth publi- 

 cation, as I am not acquainted with any other reagent which, 

 in perfectly fresh nerves, immediately renders the axis- 

 cylinder so distinctly visible. My experiment consists in 

 first splitting open the neurilemma with the needle, and 

 then, without the addition of any fluid, in gently spreading 

 out the fibres upon the glass slide. I then immediately 

 place a drop of collodion on the preparation, and cover it with 

 the thin glass. Immediately, and in all the fibres, the most 

 beautifully defined axis-cylinders are rendered apparent; 

 the medullary matter assuming a fine, granular aspect.* — Dr. 

 Edward Pfluger. 



High Powers —In a foot-note to p. 145 of the " Proceed- 

 ings of the Microscopical Society," published in No. XXXI 

 of the Journal, it is stated that Mr. Wenham has constructed 

 an object-glass of -^th of an inch focal length. 



This announcement was, doubtless, hailed with much 

 satisfaction by all who, like myself, believed that the 

 microscope had not yet reached the useful limit of ampli- 

 fying power, and microscopists are much indebted to Mr. 

 Wenham for his continued exertions in the improvement of 

 the instrument. 



It is not, however, with a view to flatter Mr. Wenham 

 that I now write, but to remind that gentleman that it will 

 depend mainly, if not entirely, upon the discoveries he may 

 be able to announce, whether the use of these high powers 

 shall be limited to himself or become available to all who 

 may be able and willing to incur the expense. I have been 

 informed that our best makers declare there is nothing to be 

 gained by the use of higher powers than those they now make, 

 and yet Beck and Co. supply two, Ross three, and Powell 

 and Lealand four additional eye-pieces to increase the 

 power of the object-glass ! although they know that, even 

 with their excellent workmanship, power is only gained in 

 this way at the expense of light and (too often) of defini- 

 tion. This seems in contradiction to their declaration. If 

 nothing be really gained by increase of power in the object- 

 glass, why give us anything beyond the first or, at most, 

 second eye-piece ? The truth, however, I believe, is this. Eye- 

 pieces are easily made, and their small price places them within 

 the reach of all ; but to increase the power of the object-glass 



* "Reichert and Du Bois Rcymond's ' Archiv u. d. Anat. Physiol.,' 1S59, 

 p. 132. 



