Calcification. 217 



upon the assumption of a previous fatty degeneration of these 

 structures, soaps of lime being formed primarily by combination 

 of lime brought in solution by the juices permeating the altered 

 tissues with the fatty acids. These soaps are later further changed 

 by substitution of the fatty acids by carbonic acid and phosphoric 

 acid. Wells {Jour, of Med. Research, 1906, X. S. ix, p. 491) can- 

 not find evidence of constant and important occurrence of these 

 soaps as a stage in the process, although in traces he finds such 

 soaps to exist in areas of calcification. Fischler and Gross (Zieg- 

 ler's Bcitragc, 1905, Festschrift fiir Arnold, p. 326) have also 

 found evidence of the presence of such soaps in atheroma and in 

 the margins of infarcts, but not in caseous areas, and are unable 

 to definitely declare that soap formation is an essential stage in 

 calcification. Wells regards pathological calcification as probably 

 essentially similar to normal deposition, and inclines to the idea 

 that there exists or is produced in the area some substance having 

 particular affinity for calcium, although he is unable to indicate its 

 nature ; it is not. however, dependent upon the vital state, as in 

 cartilage it exists both when the cartilage is Hving and after 

 it is boiled.] 



In distinction from physological calcification, in which a perfectly 

 homogeneous combination of the lime with the matrix obtains, patholog- 

 ical calcification is manifested on microscopic examination by the presence 

 of fine, highly refractile granules, looking like particles of fat and pig- 

 ments, which, with direct light (complete closure of the ■ substage dia- 

 phragm), have a dull, glistening, whitish appearance, and are found both 

 within and between the cells. On the addition of acids (especially hydro- 

 chloric acid) the calcium salts are dissolved and the presence of calcium 

 car'conate is indicated by the immediate effervescence (carbonic acid). With 

 pure sulplniric acid great numbers of crystals of gypsum (calcium sulphate ) 

 separate in delicate pointed crystals, scattered all through the tissue. A 

 calcified tissue (the same in case of partial calcification) takes a very 

 intense dark blue stain with ha?matoxylin. 



Ossified tissue differs from merely calcified structures by the forma- 

 tion of lamellae of the matrix (Haversian lamcllre) and the inclusion 

 of the bone cells in the intricately branched lacunae. 



Petrification of tissues renders them as hard as bone and gives 

 them a dirty white appearance. As a senile change this is occasion- 

 ally met as spots isolated in the cartilaginous nasal septum in cattle, 

 in the laryngeal cartilages of dogs, and quite uniformly in the costal 

 cartilages of old animals. (These foci become easily visible as 

 opaque points on drying the cartilage.) With much less frequence 

 than in man, calcification of the vessel walls is observed in animals 



