436 



CALCIFICATIOX, COXCRETIOXS, AND INCRUSTATIOyS 



is likely to be replaced by bone, no matter what tissue may be in- 

 volved ; apparently the presence of calcium salt deposits in any part 

 of the body can stimulate the connective tissues to form bone, but in 

 the absence of calcium salts even the cells which are normally osteo- 

 genic will not form bone. 



Composition of the Deposits in Calcification.-^ — The composition 

 of the inoryaiiic salts in ealeilied areas in the body seems to be prac- 

 tically the same, if not identical, whether the salts are laid down 

 under normal conditions (ossification) or under pathological condi- 

 tions. With the blood continually passing between the bones and 

 the calcified areas, the composition of the two must inevitably become 

 similar or identical. This may be shown bj' a table giving the pro- 

 portion of inorganic salts found by analysis of normal bone, and the 

 proportion found in calcified materials.^ 



Pathological Calcification. 

 Bovine tuberculosis 



'• " (softened gland) . 



Human tuberculosis 



Calcified nodule in thyroid 

 Thrombus, human 



Nokmal Ossification. 

 Human bone (Zalesky) .... 



" (Carnot") 



" (Carnot) 



Ox bone (Zalesky) 



" " (Carnot) 



Mg3(P04)2. 



0.84 



0.9 



1.2 



1.5 



1.2 



0.85 



1.1 



1.04 

 1.57 

 1.75 

 1.02 

 1.53 



CaCOa. 



12.8 

 13.1 

 11.7 

 7.6 

 10.1 

 13.4 

 11.9 



±12.8 



10.1 



9.2 



il.9 



CaaCPO*),. 



85.9 

 85.4 

 86.4 

 90.6 

 87.8 

 85.4 

 86.5 



83.8 

 87.4 

 87.8 

 86.1 

 85.7 



Iron may be present in pathological calcification, and, according to 

 Gierke,* in the fetus the entire skeleton contains iron as far as it has 

 calcified, most at the points of active ossification. This statement 

 has been questioned by Hiick and others, who believe that most of 



2a MacCordick (Lancet, Oct. 18, 1913) has advanced the interestinij hypothesis 

 tliat calcific deposits during life exist mostly as soft masses, like unset mortar. 

 Only when sufficient accumulation of CO, occurs, as after death, or in tlie center 

 of large areas of low vitality, such as fibroids, do the deposits become hardened: 

 e. g., in a gangrenous leg the calcified vessels arc stilT and brittle, wliile higlier 

 up in tlie living tissues they are soft and ])liable. This would explain why we do 

 not more often observe fractures of calcified arteries. As yet this hy])o(hesis has 

 not received the critical tests its imi)ortance deserves. If true it will explain 

 the cases of extensive calcification of the pericardium in which the heart is so 

 encased that function would seem impossible if the deposit were rigid during 

 life. (See Trans. Chicago. Pathol. Society, 1911 (8), 109, for consideration of 

 pericardial calcification.) However, Klot/ (.lour. Med. Res., 191() (34), 495) 

 lias (|U(!stioned the correctness of MacCordick's views on the basis of the occa- 

 sional occurrciice of fractures of calcified arteries, but without experimental evi- 

 dence contradicting MacCordick. 



3 Wells, lor. fit. 



4 Vircliow's Arch., 1902 (107), 318. • 



