444 CALCIFICATION, CONCRETIONS, AND INCRUSTATIONS 



held in solution or in suspension by the proteins, either as the car- 

 bonate and phosphate themselves, or as calcium-ion-protein com- 

 pounds, or perhaps both. This suspension or solution is an unstable 

 condition, possibly only because of the extremely small proportion of 

 calcium in the plasma (about 1 : 10,000), and, therefore, capable of 

 being overthrown by increased alkalinity of the blood, changes in the 

 proteins or CO2 content, or changes in the quantity or composition 

 of the calcium salts. It is probable, from the work of Barille, that 

 the calcium of the blood exists as a soluble complex double salt, tri- 

 basic calcium-carbon-phosphate (P208Ca2H2: 2C02(,C03H)2Ca), this 

 compound being possible because of an excess of CO2. 



(2) Retrogressive changes in the tissues are a sine qua non except 

 in metastatic calcification. Hyaline degeneration, the chemical 

 nature of wliich is not understood, is a very favorable condition, as 

 also is necrosis when absorption is deficient. 



(3) In the areas that are to become calcified the circulation is 

 very feeble, the blood plasma seeping through the tissue as through 

 any dead foreign substance of similar structure, without the presence 

 of red corpuscles to permit of oxidative changes. 



We may, therefore, imagine that the deposition of calcium salts 

 in such areas of tissue degeneration depends upon one or more of the 

 following conditions: 



(1) Increased alkalinity or decreased CO? in the degenerating 

 tissues, causing precipitation of the inorganic salts in the fluids seep- 

 ing slowly through them. 



(2) Utihzation of the protein of the fluids by the starved tissues 

 so completely, because of its slow passage through them, that the 

 calcium cannot be held longer in solution. 



(3) The formation within the degenerated area of a substance or 

 substances having a special affinity for calcium. 



(4) Production of a physical condition favoring the local absorp- 

 tion of salts, the least soluble salts accumulating in excess. 



The first of these conditions seems to come into play especially in 

 metastatic calcification, already discussed. We have no evidence that 

 in degenerating tissues, much less in normal ossification, there is an 

 alkahne reaction developed; but rather the contrary, an acid reaction 

 is more usual. But, as explained below, decrease in the CO2 content 

 in calcifying tissues, especially when combined with other changes, 

 may be of importance. 



Lichtwitz24 especially has laid emphasis on the possible part played 

 by changes in the proteins in inducing calcification. He advances 

 the idea that precipitation of the colloids in the degenerated area, 

 as in caseation, decreases the amount of crystalloids which can be 

 held in solution, wherefore the least soluble salts, those of calcium, 

 arc precipitated; by laws of osmotic pressure more calcium in solu- 



" Deut.-med. Woch., 1910 (36), 704. 



