194 A. B. MACALLUM. 
the action of the acid alcohol the full effect was obtained at 
the end of twenty-four hours at the latest, when the tempera- 
ture was 85°C. With nitric acid alcohol the liberation of 
the organic iron was rapid, sections of vegetable tissue (Ery- 
thronium and Iris) giving, after a stay of ten hours in the 
reagent at 85°C., an intense reaction with the acid ferrocyanide 
mixture. Ata lower temperature the result was less marked, 
but the reaction was deeper than that obtained with sections 
treated with sulphuric acid alcohol for the same length of 
time and at the same temperature. The process of liberation 
was usually completed in about thirty-six hours. So little 
does nitric acid alcohol extract the iron it liberates that in 
sections of the ovary of Erythronium americanum kept 
for six weeks in it I found little diminution in that intensity 
of the iron reaction which sections, placed in the same fluid at 
the commencement with the others, gave at the end of two 
days. With sections of animal tissue the intensity of the 
reaction was less marked with the prolonged stay in the 
reagent, which, after four or five days’ action, slightly alters 
the cellular structures. When nitric acid alcohol is allowed 
to act on a section for a longer time than is necessary to set 
free all its organic iron, diffusion of the iron salts thus formed 
is apt to occur, especially in vegetable preparations, the cyto- 
plasm giving in such cases a reaction for iron. 
That the iron demonstrated after the use of acid alcohols is 
derived from organic compounds I have shown by numerous 
experiments. I have found that when thin sections of animal 
or vegetable tissue are covered with a large quantity of Bunge’s 
fluid and kept for three days at 35° C. or higher, the teased- 
out cells give no iron reaction when mounted with glycerine 
and ammonium hydrogen sulphide on the slide, even after two 
weeks and at 60°C. Furthermore, sections so treated with 
Bunge’s fluid, when subsequently subjected to the action of 
sulphuric acid alcohol or of nitric acid alcohol, yield no iron re- 
action whatever. Bunge’s fluid, therefore, extracts the iron which 
the prolonged application of ammonium hydrogen sulphide and 
glycerine at an elevated temperature liberates and demon- 
