PATHOLOGICAL CALCIFICATION 443 



fluids makes the calcium salts decidedly less soluble. In the stomach 

 the calcium deposits arc limited to the interglandular tissue about 

 the upixn- portion of the shmds of the fundus, exactly corresponding 

 to the parietal cells which are supposed to secrete the acid. Pre- 

 sumabl}^, under normal conditions, the amount of calcium in the 

 blood is too slight to be thrown down in this way, but when oversat- 

 urated because of the calcium absorption in the skeleton, precipita- 

 tion occurs in the parts of the bodj^ where the alkalinity of the blood 

 or tissue fluids is greatest, or the CO2 concentration least. There also 

 occurs a true metastatic calcification in the large arteries, pulmonary 

 veins, and beneath the endocardium of the left side of the heart; that 

 is, always in the places where the blood contains the least CO?. This 

 fact supports the hypothesis that the CO? is an important factor in the 

 solution of calcium salts in the blood, and that when there is an over- 

 saturation with calcium it is deposited where the CO2 is least abun- 

 dant. When the amount of calcium in the blood is increased by 

 injecting or feeding calcium salts, depositions of calcium salts may take 

 place in injured tissues, ^^ or even in normal tissues, as in Tanaka's 

 experiments.^^ Extensive calcification may take place in the lungs 

 without any evident bone disintegration, nor yet nephritis which has 

 been thought at times to lead to enough calcium retention to account 

 for metastatic calcification (Harbitz).^° A few cases of extensive 

 subcutaneous calcification of unknown etiology have been described, 

 but their relation to metastatic calcification is doubtful, as they seem 

 to be localized deposits. ^^ 



Some have attempted to include the calcification of the vessels and 

 other tissues in old age in the metastatic calcifications, ascribing the 

 origin of the salts to the senile absorption of bone, but senile calcifica- 

 tion is probably dependent rather upon the extensive hyaline degenera- 

 tion of the connective tissues that occurs in the senile scleroses,-^ a 

 change which seems to be more physical than chemical.-^ 



Chemistry of the Process of Calcification 



In analyzing the etiological factors in the production of pathologi- 

 cal calcification for the purpose of determining the chemical changes 

 that occur in the process, we have the following facts upon which to 

 base the consideration: 



(1) The calcium salts must come from the blood, where they are 



18 See Thayer and Hazen, Jour. Exp. Med., 1907 (9), 1. 



i^Biochem. Zeit., 1911 (35), 113; (38), 285; see also Katase, Beitr. path. 

 Anat., 1914 (57), 516. 



2« Norsk Mag. Laeg., 1917 (78), 1129. 



21 See Mosbacher, Deut. Arch. klin. Med., 1918 (128), 107. 



^^ Under the name of "calcium gout," M. B. Schmidt has described a case with 

 generalized deposition of calcium in other tissues than those usually affected in 

 metastatic calcification (Deut. med. Woch., 1913 (39), 59). 



^^ See analyses of elastin from calcified and normal aortas by Ameseder, Zeit. 

 physiol. Choin., 1913 (85), 324. 



