CORRESPONDENCE. 235 



pared with a binocular instrument, but these are very slight indeed, 

 and we think that considerable credit is due to Mr. Mayall, who in- 

 duced Mr. Browning to construct the instrument. 



What is the Cutisector ? — It is simply an instrument for taking 

 sections of the living skin, and is likely to prove useful to those who 

 are engaged in the study of skin diseases. It is thus described by 

 Dr. H. S. Purdon, in a letter to the ' Lancet ' (September 20th). He 

 says, I think it may be useful to call attention to the little instrument 

 known as the cutisector, the makers of which are Messrs. Tiediman 

 and Co., New York. The cutisector is an extremely handy and con- 

 venient instrument for making /rcs/i sections in various skin affections; 

 indeed it was invented principally for this purpose by my friend Dr. 

 Henry G. Piffard, of New York, and whose description of it appeared 

 in the ' American Journal of Syphilography and Dermatology,' 1870. 

 By using either spray the pain is very slight, and the ether hardens 

 the tissue, and allows us to thus obtain a better section. Recently 

 Dr. Piifard has further improved the cutisector, one of which he was 

 kind enough to send me. With it I have made many sections from 

 patients for microscopic examination, there being always a plentiful 

 supi^ly of material at the Belfast Hospital for Skin Diseases, especially 

 (not to mention others) in one case of scleroderma, which is a rare 

 disease, I obtained good sections of diseased skin. The cutisector is 

 far over Valentin's knife or thin sections made with a razor, in which 

 case the preparation to bo examined with the microscope requires to 

 be first immersed in some hardening solution, usually of chromic acid, 

 or imbedded in wax, before a sufficiently thin section can be obtained. 

 The little incision made by the cutisector heals at once, and if it is 

 inclined to bleed I brush it over with some stypic colloid. Of course 

 any thickness of skin may be obtained, as the blades of the instrument 

 can be closed or separated by a screw as required. 



COERESPONDENCE. 



Cause of Colour in P. foemosum in using the Older 

 Immersion Objective. 



To the Editor of the '■Monthly Microscopical Journal.' 



SiK, — Since I sent you the audi alteram partem letter (see last 

 number, pp. 151, 152) complaining of the want of perfect achromatism 

 in the immersion ^V^^ object-glass, I have received the enclosed letter 

 from the makers, which so fully and lucidly explains the cause of it, that 

 I think it would be a dereliction of duty to neglect its immediate publi- 

 cation : more especially as this is probably the only way in which your 

 readers will obtain the information ; as it is a plan of Messrs. Powell 

 and Lealand (and a most excellent one it is) never to notice (publicly) 

 any remarks upon their work ; but to act on the principle of the i)ro- 

 verb, " Do well, and let the world talk." 



In fact, if they were to undertake to reply to all the attacks of 



