IRON COMPOUNDS IN ANIMAL AND VEGETABLE CELLS. 217 
balsam, it was always found that the spherical elements ex- 
hibited an intense stain, while the remaining parts of the 
spherules were absolutely uncoloured. I found it possible to 
demonstrate this and the reaction for iron in the same pre- 
paration. When the “ white” spherules, fixed with heat, were 
kept in slightly warm sulphuric acid alcohol for twenty-four 
hours, their spherical elements gave, on treatment with an acid 
ferrocyanide solution, a Prussian blue reaction, and, when sub- 
sequently stained with asafranin solution, became violet. These 
results show how close is the relationship between the sub- 
stance composing the spherical elements and chromatin. 
A few of the spherical elements in the “ white ” spherules 
are not of the character described, for in preparations made 
with Flemming’s fluid one finds, now and then, a spherule in 
which one or more large droplets of fat are demonstrated by 
the intensely black reaction of the osmic acid. Apart from 
the occurrence of these, there is comparatively little fat in 
the “ white” spherules, a fact strikingly shown when a thin 
section of the hard-boiled yolk, embracing portions of the 
*‘ white” and “ yellow” zones, is submitted to the action of the 
reagent for twenty-four hours, the ‘‘ white ” then exhibiting a 
greyish appearance, while the “ yellow ” area is almost black. 
The “‘ yellow” spherules are also richly supplied with the 
iron-containing compound, but this is quite differently distri- 
buted from what it is in the “ white” zone. The appearances 
of these are subject to a great deal of variation. Some contain 
only large round granules, in others the granules have a puncti- 
form character, while in others again both kinds of elements 
may be mingled with minute fat droplets. Owing to differ- 
ences in the specific gravity of the constituents apparently, 
the granules may be found, in some cases, to be gathered in 
one portion of the spherule, the remainder of the contents 
being occupied by a clear, non-granular substance of a firm 
consistence, a character resulting from heat coagulation. Itis 
in such spherules as these that one determines distinctly how the 
iron compound is disposed, for, in those in which the granules 
are uniformly distributed, it is sometimes exceedingly difficult 
