( 410 ) 
The ordinary means to tinge nuclei: haematoxylin, alum-carmine 
and different aniline-stains produced a diffuse colouring, whereas 
only after having been for about fourteen days in pikro-carmine the 
nuclei became visible. 
Then however the protoplasm of the cells had disappeared; it 
could not be otherwise than dissolved in the alkaline pikro-carmine, 
and it seemed only natural rather to take a neutral solution of this 
tincture. I tried different prescriptions, but I was not successful in 
finding a neutral solution: a moist red litmuspaper hung in the 
bottle above the liquid, was tinged blue after a few hours. 
PauLt MAYER in his article: “Ueber Pikrocarmin” ') says not to 
believe that: “Carmin in einer ganz neutralen Fliissigkeit, die noch 
dazu eine relativ grosse Menge pikrinsauren Salzes enthält, gelöst 
bleiben kann” (Le, p. 19). He examined pikro-carmine from the 
anatomical laboratory at Munich and trom the Collège de France, 
moreover liquid and solid samples of GRÜBLER and different solid 
samples of MERCK. 
The pikro-carmine is a solution of two solids: picrate of ammo- 
nium and ammoniumcarmine — the discoverer RANVIER believed 
it to be a chemical combination, but this is an assertio gratuita — 
and now it is (leaving the alkaline reaction out of the question), a 
deficiency of most prescriptions that they cannot specify the relative 
proportion of these elements and leave it to the inconstancy of chance. 
This is the case with all prescriptions in which bacteria from the 
air are called to aid, according to the method followed in the Collége 
de France *), moreover the preparation then lasts several months, 
and, as experience has taught me, there is considerable danger of 
obtaining a totally useless product. 
Because of the difficulties just mentioned and others besides, PAUL 
MAYER says at the end of his article (l.c, p. 28): „Das Facit wäre 
also: das Pikro-carmin gehört zu den Färbmitteln, die eine bewegte 
Vergangenheit hinter sich haben, und von denen man möglichst 
wenig Aufhebens mehr machen sollte.” 
Pikro-carmine can however not yet be considered out of date 
as a stain in microscopical technics, and I have been successful 
in preparing in a simple way a liquid, which may practically be 
called neutral, at the same time containing fully known quantities 
of picrate of ammonium and ammoniumearmine. The method can 
*) Paut Mayer, “Ueber Pikrocarmin”, Zeitschrift fiir wissenschaftliche Mikroskopie 
und mikroskopische Technik. Bd. 14, 1897. 
*) See A. Boutes Ler, The Microtomist's Vademecum, fourth Ed. 1896, p. 153. 
