196 
PIERRE A. FISH. 
because of their solubility, are, therefore, most easily absorbed 
by the plants. 
The phosphate of iron is insoluble in water, or in water con¬ 
taining carbonic acid, and becomes soluble only under certain 
complex conditions, so that its use by the plants is compara¬ 
tively limited. 
Distribution of Phosphates in Animal Tissues .—In the tis¬ 
sues of living beings five forms of phosphates are encountered, 
namely : the phosphates of potassium, soda, lime, magnesia and 
iron. 
These phosphates are unequally distributed in each kind of 
tissue, but some particular one of them may predominate in a 
certain organ, or a particular organic system. Thus, the phos¬ 
phate of potassium predominates in the nervous system ; the 
phosphate of sodium predominates in the blood plasma ; the 
phosphate of iron in the red corpuscles; the phosphate of mag¬ 
nesia in the muscular tissues, and the phosphate of lime in the 
bones. 
The soluble alkaline phosphates are more especially present 
in organic liquids or tissues of soft consistence. The phosphate 
of soda in the plasma (liquid), the phosphate of potassium in 
the nervous system (soft consistence). 
The insoluble earthy phosphates are more especially re¬ 
served for the solid tissues. The phosphate of magnesia asso¬ 
ciated with the phosphate of soda and phosphate of lime pre¬ 
dominates in the muscles (semi-solid), the phosphate of lime is 
in excess in the bones (solid). 
Elimination .—The phosphates, thus generally distributed 
through the great tissue systems of the animal body, are influ¬ 
enced by all metabolic processes, and, like other compounds, 
are being torn down and built up as the result of physiological 
activity. Pathological conditions, affecting any of these sys¬ 
tems, by interfering with the anabolic or katabolic functions, 
influence, one way or the other, the elimination of the products 
of metabolism. 
The two principal channels for the elimination of the phos- 
