IRON COMPOUNDS IN ANIMAL AND VEGETABLE CELLS. 195 
strates, and with this removal disappears the iron demonstrable 
after treatment with either of the other acid alcohols. This 
shows that the iron in such cases cannot be derived from the 
reagent nor from the glass of the vessel used, and this is em- 
phasised by the results of other experiments. I extracted with 
Bunge’s fluid all the iron from a series of sections of an ovary 
of Erythronium, and then subjected these to the action ofa 
large quantity of sulphuric acid alcohol for twenty-four hours 
at 85° C. These gave no iron reaction, while others did so 
which had not been treated with Bunge’s fluid, and which were 
put in the acid alcohol at the same time. That the absence of 
an iron reaction was not due to a lack of absorptive capacity 
on the part of the section, brought about by Bunge’s fluid, 
was proved when such sections were allowed to stay in sulphuric 
acid alcohol containing a little ferric salt in solution! for half 
an hour. The reaction obtained was marked, and almost wholly 
confined to the nuclei. These experiments were repeated 
again and again with sections of animal and vegetable tissues, 
and the results were always the same, proving that the iron 
demonstrable after acid alcohol has been used on tissues is 
derived from the latter, and not from the reagent or the vessel 
used. These experiments indicate, however, how necessary it 
is, in investigating the distribution of iron in tissues, that the 
reagents should be absolutely free from iron, and that, in 
sections of tissues containing iron in an inorganic or albuminate 
form, there is danger, when either sulphuric acid alcohol or 
nitric acid alcohol is used upon them, of its redistribution, and 
especially of its deposition in those parts of the cell which 
absorb various compounds readily. In order to guard against 
this, I found it advisable to steep the sections in a quantity of 
Bunge’s fluid for a time which varied with the temperature at 
which the reagent was applied, as, for example, for one to 
two hours at 50°—60° C., but for eight to ten hours at 35° C. 
1 This solution was made in the following way. A quantity of sulphuric 
acid alcohol was allowed to act on ferric oxide in powder for about a week, 
when a portion passed into solution as a ferric salt. Of this solution 1 e.c. 
was taken and added to 10 ¢.c. of pure sulphuric acid alcohol. 
