CHEMISTRY OF THE PROCESS OF CALCIFICATION 369 



fore, capable of being overthrown by increased alkalinity of the 

 blood, changes in the proteids, or changes in the quantity or 

 composition of the calcium salts. 



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

 Hyaline degeneration, the chemical nature of which is not under- 

 stood, 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 any one 

 of the following conditions : 



(1) Increased alkalinity in the degenerating tissues, causing 

 precipitation of the inorganic salts in the fluids seeping slowly 

 through them. 



(2) Utilization of the proteid 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 absorp- 

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



The first two ideas have little indeed to support them, and 

 are mentioned chiefly because they have been advanced in the 

 past by certain writers. The possibility of the formation of 

 calcium-binding substances within the degenerated area has 

 always seemed the most attractive, and has received the most 

 attention by investigators. Of the special substances that 

 might be present in such areas that would have a high affinity 

 for calcium, phosphoric acid usually receives first consideration, 

 since it is as phosphate that most of the calcium is bound, and 

 also since the possible sources of phosphoric acid in decomposed 

 nucleoproteids and lecithin are so obvious. Less considered in 

 the past, fatty acids offer another possibility, especially in view 

 of the fatty degeneration that so frequently precedes calcifica- 

 tion. Proteids might also be formed that would combine cal- 

 cium, especially deutero-albumose, which Croftan : states has a 

 high degree of affinity for calcium, and which would be present 

 in areas undergoing autolysis. 



1 Jour, of Tuberculosis, 1903 (5), 22. 



