IRON COMPOUNDS IN ANIMAL AND VEGETABLE CELLS. 189 
the employment of ammonium sulphide, succeeded in obtain- 
ing some interesting results which necessitated control experi- 
ments based on the removal of all traces of inorganic com- 
pounds of iron from the tissues under investigation. for 
this purpose Bunge’s fluid was used, and it was thought that 
hardened specimens of the ovary, when subjected to its action 
for a time, would not give, on the addition of ammonium 
sulphide, any immediate reaction for iron, and that further 
treatment with the latter reagent in a warm oven for several 
days would show the presence of iron in the nuclei of their cells, 
and possibly also in their cytoplasm. Much to our surprise, 
however, the treatment of the ovary of Erythronium with a 
quantity of Bunge’s fluid for two weeks at 20°C., and the 
subsequent application of ammonium sulphide, resulted in the 
production of a marked reaction for iron, which under the 
microscope was found confined to the nuclei. I was at first 
inclined to believe that the iron so shown was due to diffusion 
into the nuclei of that present in an inorganic form in the 
tissues, and this would appear to be Gilson’s view; but repeated 
experiments have demonstrated the incorrectness of this 
explanation, and that Bunge’s fluid liberates the iron of organic 
compounds.! Experiments were also made on animal tissues 
and similar results were obtained. The liberation of the iron 
is to be attributed to the hydrochloric acid, the only active part 
of the reagent. This conclusion suggested a number of 
experiments, all based on the principle that whatever proper- 
1 Gilson’s statement is difficult to interpret. He does not say whether he 
applied the reagent to sections of tissues or to the latter in mass, and at what 
temperature it was allowed to act. He appears to regard the iron absorbed 
by dead nuclein as combined with the latter, and he remarks, in reference to 
my statement that Bunge’s fluid removes all inorganic and albuminate iron 
from sections after treatment with it for ten hours: “but I have observed 
that Bunge’s liquid does not take away the iron artificially combined with 
dead nuclein after six days.” I can explain his statement only on the sup- 
position that he used the reagent on the tissues in mass, and that he thereby 
obtained the same results that I did under similar circumstances; in other 
words, the iron “artificially combined with dead nuclein” was in reality iron 
liberated by Bunge’s fluid from its masked condition in the chromatin and re- 
tained by the latter. 
