188 A. B. MACALLUM. 
a part of the iron of the hematin is precipitated as a greyish- 
white hydroxide, which, if filtered off, gives at once with 
ammonium sulphide the greenish-black sulphide reaction. 
Very weak solutions of hydrochloric and other acids effect the 
removal of the iron, and if solutions of hematin in alcohol are 
kept for a week or more in contact with solutions of various 
salts (potassium chlorate and sulphate and sodium chloride 
and phosphate), decomposition of the hematin results, and 
iron is liberated as an inorganic compound. In all these 
respects hematin behaves like the ferrocyanides, while it differs 
markedly from haemoglobin in the same points. 
Experiments show, however, how little, if any, of the iron 
demonstrated in animal cells is derived from hematin. Sec- 
tions of the liver and other organs of Vertebrates, as well as of 
vegetable tissues, were placed in alcoholic solutions of hematin 
for twenty-four hours, then washed in alcohol for a few minutes, 
and kept in a quantity of the glycerine and sulphide mixture 
at a temperature of 35° C. for twenty-four hours. At the end 
of the latter interval all the sections were blackened, and 
under the microscope the nuclei were dark green from the 
ferrous sulphide liberated from the hematin absorbed by the 
chromatin. In order to get this result the sections do not 
require to be teased out at all. The rapidity with which such 
a strong reaction is obtained indicates that in ordinary teased- 
out cells mounted on the slide in the glycerine and sulphide 
mixture, the deep reactions obtained after several days or after 
a week are due to a decomposition, not of hematin, but of 
some other compound or compounds. 
Ammonium hydrogen sulphide, then, may be regarded as a 
reagent of very great value in the investigation of ‘‘ masked ” 
compounds of iron, and it must constitute a final test for this 
purpose, whenever the accuracy of the other reagents, used 
also for determining the distribution of assimilated iron com- 
pounds in cells, is called in question. 
In June, 1891, Mr. R. R. Bensley, while carrying on under 
my direction a research on the distribution of iron in the 
ovary of Erythronium americanum, as demonstrated by 
