CONCRETIONS 375 



developed. Stoltzner, 1 finding evidence that rickets does not 

 depend upon either lack of calcium in the food or deficient ab- 

 sorption of calcium, and that the blood in rickets is of normal 

 alkalinity, looks upon the failure of calcification as depending 

 upon an abnormality in the calcified bone tissue itself. He 

 finds evidence of a preliminary alteration in normal osteoid 

 tissue which prepares it to take the salts out of the blood, and 

 Pfaundler 2 supports this view, suggesting that this preparatory 

 ohange in the osteoid tissue may depend upon autolysis, which 

 is perhaps deficient in rickets. 3 



CONCRETIONS 



All pathological concretions appear to be laid down according 

 to a definite law. There must first be a nucleus of some sub- 

 stance different from the substance that is to be deposited, and 

 which is most frequently a mass of desquamated cells, but may 

 consist of clumped bacteria, masses of mucus, precipitated pro- 

 teids, or a foreign body of almost any sort. Upon this nucleus 

 substances crystallize out of solution, much as cane-sugar crys- 

 tallizes on a string to form rock candy, but with the impor- 

 tant exception that among the crystals is usually deposited 

 more or less mucin or other organic substance, which forms 

 a framework in which the crystals lie, and which remains, if the 

 crystals are dissolved out, as a more or less perfect skeleton 

 of the concretion. In no case would the concretion form were 

 it not that the solution is overcharged with some substance, but 

 not infrequently it is the presence of the nucleus that leads to 

 the precipitation of the substance ; i. e., the nucleus may play 

 either a primary or a secondary role. With few exceptions, the 

 dissolved substance is deposited in crystalline form, although 

 the crystalline structure may in time partly disappear through 

 condensation or through filling of the interstices with some 

 other material. Even so structureless a substance as amyloid 

 may, when forming concretions, appear in a crystalline form 

 (Ophiils). The structure of a concretion depends upon two 

 factors : The crystals tend to be deposited at right angles to 

 the surface, and thus give a radiating structure ; but the rate of 

 deposition is usually irregular, and during the periods of quies- 

 cence the surface tends to become covered with mucin or other 

 organic substances, hence we also get a concentric, laminated 



1 Jahrb. f. Kinderheilk., 1899 (50), 268. 



2 Loc. eit. 



3 See also Nathan, Med. News, 1904 (84), 391. 



