440 CALCIFICATION, CONCRETIOXS, AND IXCRUSTATI0X8 



of tlie ealciiim 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-earbon-phosphate (PoOgCa,!!, : 2COo(C03H)2Ca), this 

 compound being possible because of an excess of CO,. 



(2) Retrog-ressive changes in the tissues are a sine qua non. Hya- 

 line degeneration, the chemical nature of which is not understood, is 

 a veiy 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 dei)osition 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) Utilization 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 tlie 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 

 alkaline reaction developed ; but rather the contrary^ an acid reaction 

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

 in calcifying tissues, especially when combined with other changes, 

 may be of importance. 



Lichtwitz ^^ 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, tliose of calcium, 

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

 tion will then enter to establisli ('()uilibrium, be precipitated, and 

 make way for more calcium, until the amount of deposit prevents 

 further osmotic diffusion. Altliough suggestive in regard to patho- 

 logical calcification, and probably of importance in the fonnation 

 of concretions, this conception is difficult to aiii)ly to normal ossifi- 

 cation ; also in pathological calcification one would exjiect precipi- 

 tation of calcium to occur in tlie outermost surface of the degener- 



11 Doiit. mcd. Wocli., 1010 (aO), 704. 



