BIOLOGY: H. S. WASHINGTON 
623 
AN APPARENT CORRESPONDENCE BETWEEN THE CHEM- 
ISTRY OF IGNEOUS MAGMAS AND OF ORGANIC 
METABOLISM 
By Henry S. Washington 
GEOPHYSICAL LABORATORY, CARNEGIE INSTITUTION OF WASHINGTON 
Received by the Academy. October 5, 1916 
In a recent paper^ it was shown that potassium and magnesium on the 
one hand, and sodium and iron on the other, tend to vary together in 
igneous magmas and the minerals formed from them. That is, igneous 
rocks and minerals which are high in potassium contain, (of the two), 
much magnesium and but little iron; while if the rock or mineral is 
dominantly sodic iron will be high and magnesium low, if these are 
present. This relation seems to be independent of the silicity (amount 
of silica) and but slightly modified by the amount of calcium. 
The object of the present note is to call attention to what appears to 
be a congruous relation of these pairs of elements in the organic world 
— briefly stated, it would appear that, of the four, iron and sodium are 
necessary for animal metabolism, (magnesium and potassium very much 
less so); while magnesium and potassium are essential to vegetable 
metabolism, the other pair being of minor importance. 
This correspondence is indicated by the following considerations, all 
of which are well-known to biologists, so that it is only in their collo- 
cation and the pointing out of an apparent congruity in the chemistry 
of the mineral with the animal and vegetable kindgoms that there is any 
novelty. 
It is well-known that the blood pigments of the higher animals, hemo- 
globin and its congeners and derivatives, are protein bodies which con- 
tain iron as an essential constituent, and it has been suggested^ that this 
element acts as the oxygen carrier in the vital processes in which the 
blood plays the all-important part. In the blood plasma sodium is an 
important constituent, its amount being several times that of the potas- 
sium, though the latter element is, apparently, more important in the 
cells. The amount of magnesium in the plasma is also very small. 
As stated by one authority^ it would appear that ''potassium com- 
pounds are replaced in the [animal] organism by sodium chloride," and 
that as a consequence ''common salt is, not only a condiment, but a 
necessary addition to the food." The universal and necessary use of 
sodium chloride in food by man and many of the higher animals need 
only be mentioned. 
