Lime and magnesia are indubitably quite as effective agents in the control of ammonia as sulphur is in the control of phosphorus.  If we consider the minerals as the foundation and mortar which give stability to the vital machine, leaving out chlorine and fluorine, we find that iron, manganese, potash, soda, and silicic acid play this role.  Sulphur, because it possesses the property of becoming gaseous, is able to take part directly in the formation of albumen, that variable basis of body material, whereas all of the other mineral substances except silicic acid can only be assimiliated in so-called binary compounds in the form of salts.

I will give a brief review of them, beginning with iron, as thus the significance of augmentation of the mineral content of vegetables and small fruits and eggs will be made much clearer.

Normal blood albumen is essentially a compound of calcium and sodium into which iron and sulphur both enter.  A deficiency of calcium commonly makes itself known by dental defects, just as lack of sulphur reveals itself by the falling out and poor growth of hair.  Insufficiency of iron in the blood is evidenced, apart from lack of spirit, by paleness of face and blue lips; insufficient sodium by glandular tumors and abnormal cartilaginous growths.

The entire amount of iron in the blood of an adult person is, on the average under normal conditions, four grams, as much as a nickel weighs.  We may well judge that this amount is not sufficient to set the motive power of our bodies in action, if we overlook that complex factor the circulation of blood.  The left side of the heart has the capacity of containing about six ounces of blood, and every heart beat drives this amount through the aorta.  With seventy beats to the minute, twenty-five pounds of blood is pumped from the heart every minute.  What is the result?  That the four grams of iron keep up such an incessant movement that they pass from the heart into the aorta sixty times an hour or 1440 times in 24 hours.  It may be asserted, therefore, that in 24 hours 13 pounds of iron (that is 1440x4 grams) pass from the heart into the aorta.  Can it be doubted, in view of this, that the iron serves to produce an electro-dynamic force?

In respect to the generation of electricity, it matters not whether there be an entirely new supply of iron passing a given point, or whether the same iron pass that point anew each minute.  Two factors work together in the circulation of the blood, namely, the active attraction of nerve tissue and the passive susceptibility of the blood contents to that attraction.  Faraday has conclusively shown that blood is magnetic in character because of the iron it contains.  If four grams of iron is the normal quantity in the blood, it is clear that the reduction of this amount, say by two grams, will lessen its susceptibility and slacken its circulation.  The electrical nerve ends will then strain in vain for the electricity which the blood current should yield, and the result will be neuralgia.