CALCIFICATION. 53 



ill this way ; finally, we often find those small globular portions 

 of cartilage, with which we are familiar, on the one hand as 

 constituent elements of enchondromata, on the other as out- 

 growths from articular cartilages and synovial membranes, im- 

 pregnated with earthy salts. In every one of these cases the 

 calcareous deposit first appears in the central parts of the carti- 

 laginous structure, in those which are farthest from the surface, 

 where the circulation of nutrient fluid is most hindered, perhaps 

 even totally arrested. Provisionally, therefore, we are justified, 

 on pathological grounds, in assuming that the precipitation of 

 calcareous salts results from a retardation or stagnation of the 

 nutrient fluid. 



§ 54. In studying the histological details of calcareous in- 

 filtration, we will avail ourselves first of the admirable example 

 afforded by the development of cartilage. Cartilage is a con- 

 nective substance, made up of cells and an intercellular matrix. 

 We cannot as yet tell why it is that calcification sometimes 

 begins in the cells, sometimes in the intercellular substance. 

 Suffice it to say that either may be first affected ; indeed, it is 

 characteristic of this, as of other forms of infiltration, that the 

 most diverse structural elements are liable to be involved. 



The first visible effects of calcification are the so-called 

 earthy granules (Kalkkriimel) small, roundish or angular particles, 

 which appear black by transmitted, white and glistening by 

 reflected light, and which are imbedded more or less thickly in 

 that part of the cartilage (say its matrix) which is primarily 

 involved. Attempts have been made to show that these particles 

 are actually the earthy salts, and to demonstrate crystalline form 

 in them ; this, however, was a mistake. The earthy granules 

 may, indeed, owe their leading properties, their density, their 

 whiteness and opacity to the calcareous salts with which they 

 are impregnated ; nevertheless we must distinguish in every 

 granule — first, a particle of the matrix of equivalent size ; and, 

 secondly, the earthy salts which it contains. Without this dis- 

 tinction, or rather generalisation, the subsequent changes would 

 be not merely inexplicable, but utterly impossible ; for after the 

 matrix has first of all been darkened by the calcareous granules, 

 it assumes in the sequel a homogeneous lustre, such as we find 

 in the matrix of bone, this appearance being clearly due to the 

 mutual approximation of the calcareous granules, and their ulti- 



