438 dALCIFICATION, CONCRETIONS, AND INCRUSTATIONS 



OCCURRENCE OF PATHOLOGICAL CALCIFICATION 



As far as we know, calcification seldom occurs in normal tissue, 

 except in the formation of bone. Often the infiltrated tissue is com- 

 pletely dead, as in infarcts, organic foreign bodies, caseous areas, and 

 particularly in old inspissated collections of pus. It may be said 

 that any area of dead tissue that is not infected, and that is so large 

 or so situated that it cannot be absorbed, will probably become infil- 

 trated with lime salts. i\Iost frequently calcified, next to totally ne- 

 crotic tissues, are masses of scar-tissue that have become hyaline sub- 

 sequent to the shutting off of circulation in the scar by contraction 

 of the tissue about the vessels. Elastic tissue also seems prone to an 

 early calcification, and it is not uncommon to see the elastic laminaB 

 of small arteries calcified in an apparently selective manner. A pe- 

 culiar form of calcification is that frequently found in ganglion-cells 

 of the brain which have become degenerated or necrotic, particularly 

 in the vicinity of old hemorrhages; the cells become infiltrated with 

 lime salts until a complete cast of the cell, with dendrites and axis- 

 cylinder well impregnated, is formed. The calcification of renal epi- 

 thelium obtained experimentally by temporary ligation of the renal 

 vessels or by the administration of certain poisons, is more closely 

 related to the formation of ordinary urinary eoneretions than to tissue 

 calcification, the calcium being present as the phosphate only.^^ Cal- 

 cification of epithelial cells does occur, however, and seems to be pre- 

 ceded by hyaline changes, in which hyaline substance the calcium is 

 later deposited, as in epithelial pearls, for example. 



Metastatic Calcification. — What is perhaps the only exception to 

 the rule that some form of tissue degeneration is required before cal- 

 cification occurs, is the ''metastatic calcification" of Virchow.^- In 

 conditions with much destruction of bone, as osteomalacia, caries, 

 osteosarcoma, etc., deposits of lime salts have been found distributed 

 diffuseh^ in various organs, particularly in the lungs and stomach. 

 As much as 13.38 per cent, of the dry weight of the lung and 12.15 

 per cent, of the kidney have been found as CaO in such a case.^--'' 

 As there is no evidence that these organs have been the site of any dif- 

 fuse tissue necrobiosis before the calcification occurred, it seems prob- 

 able that the deposits have been made in practically or quite normal 

 organs, because of oversaturation of the tissue fluids by calcium salts. 

 The fact that the lung and stomach, and also to a less degree the kid- 

 ney, are picked out, suggests that the calcification is related to the 

 fact that in these same organs we have the excretion of acids into 

 their cavities, which leaves the fluids in the substance of the organs 



11 Jour. Med. Researeli. 1011 (2.")), :17.1. 



12 Virohow'a Arrli.. IS.'i.'S (S), 10.3: review by Koekel. Dent. .\reh. klin. IMed., 

 1899 (64), 332. Biblioj,r,aphv and review bv Wells, Arch. Int. Med., 1015 (15), 

 574. 



i-'a Virchow's .\rcli., 1000 (107), 112. 



