Calcareous Infiltration Or Calcification refers to the deposit of earthy salts within the tissues. It occurs in consequence of a deficiency of oxygen and an excess of carbon dioxid in the tissue juices, which causes a deposit of the carbonates and phosphates of magnesium and calcium. Oxalates are also generally present.

This process is found only in those tissues that are either completely destroyed or else undergoing degeneration as a result of imperfect nutrition.

The deposition of the salts is probably due to a lack of oxygen and an increase of carbon dioxid in the tissues, on account of which there is a precipitation of the magnesium and calcium carbonates and phosphates.

It is commonly seen in the fibrous framework, but may be found within the cells as well. The favorite site is in the connective tissues that have a poor blood-supply, such as cartilages, the walls of blood-vessels, also in old inflammatory areas, in regions of degeneration, such as infarcts, around foreign bodies, and in tumors, particularly in degenerated uterine fibroids. Is sometimes seen in the ganglionic nerve-cells, in the "pearls" of epitheliomata, and in the tumors of the nervous system called psammoma, which are made up of masses of salts deposited in the tissues. The most common seat is probably in the arterial system. It is often the sequel of a senile atrophy of the elastic tissue of the vessel wall, along with degeneration of the connective tissue and a general fibrosis.

Fig. 13. - Calcareous Infiltration of the Wall of a Small Artery From the Wall of a Gumma of the Liver. Zeiss, Oc. 2; ob. D. D. (McFarland).

In addition to the calcification that has occurred in the media contiguous to the fenestrated elastic layer, there is marked syphilitic endarteritis with great reduction in the caliber of the vessel from proliferation of the subendothelial tissue of the intima.

The valves of the heart frequently undergo calcification, as well as the walls of the aorta, the coronary, and cerebral arteries.

Microscopically the salts may appear as granules, spicules, plates, or crystals.

If within the cellular protoplasm the granules may be so numerous as to hide the nucleus.

The salts are insoluble in ether, but give off carbonic acid gas when dissolved by hydrochloric acid. They also stain very deeply within hematoxylin.