110 THE AMERICAN MONTHLY [Apr., 



formalin upon my hands two or three times, immediately 

 washing it off, without any injury to the skin but after 

 the [>rolong'ed (A hour) handling of tissues hardened in a 

 2^ per cent solution of formic aldehyde, one day I found 

 the skin considerably roughened and somewhat be- 

 numbed for a day or two. 



We have used the pure formalin in the place of nitric 

 acid in a few cases of primary venereal sores and here 

 some little pain was occasioned lasting longer than in 

 the case of the acid, but causing no other bad results, 

 the sores healing earlier considerably than in cases not 

 so treated. Still on account of the pain I think it would 

 be better to apply a diluted solution and repeat the ap- 

 plication if necessary. The secondary symptoms in the 

 cases of syphilis were of course not prevented : in those 

 of chancroid there was no autoinoculation. 



As regards the hardening and preservation of tissue 

 I have used formalin to the exclusion of Mueller's lluid 

 and alcohol recently and am much pleased with it. A 

 block of tissue -^ or $ inch in thickness can be hardened in 

 24 hours or less in pure formalin without the great shrink- 

 age in cells that occurs in the use of absolute alcohol. 

 Even a 1 per cent solution acts quicker than Mueller's 

 tiuid and w ill preserve large specimens but as a harden- 

 ing agent I prefer a stronger solution 5 per cent to 10 per 

 cent which, except in the case of very loose tissue such as 

 lung, renders a ^ inch block firm enough to cut within 

 48 hours. With a 10 per cent solution the blood and col- 

 oring matter seem to be fixed in the tissue so that com- 

 paratively little bleaching occurs ; with a 1 per cent solu- 

 tion at the outset the bleaching appears to me to take 

 place to nearly or quite the same extent as it does with 

 alcohol. 



I at first thought that the tissue rapidly fixed in forma- 

 lin might be soaked in warm liquified gelatine or agar, 

 imbeded in one of these media, exposed to the vapor of 



