2i6 Retrogressive Processes. 



turbances. Each pigment particle is essentially a foreign body 

 and indnces a certain amount of inflammatory reaction, usually of 

 low grade and productive of an increased amount of fibrous tis- 

 sue. Parts the seat of marked pigmentation, as the lungs and 

 bronchial glands, become more or less indurated. The possibility 

 of infection by tuberculosis, especially noted in man, becomes more 

 easy when previous dust inhalation has induced a chronic bron- 

 chitis and has induced the secondary faults of pulmonary blood 

 and Ivmph drainage and has lowered the general vital resistance of 

 their tissue b\- a prolonged chronic interstitial inflammation. In 

 less important organs than the lungs, of course, the changes occa- 

 sioned by external pigmentary deposit are proportionately less 

 serious.] 



Calcification and the Formation of Calculi. 



Calcium salts are normally present in solution in the body 

 fluids (calcium glycerin-phosphate, carbonate, lactate, oxalate, etc.). 

 Deposition of lime in solid form takes place normally in the bones 

 and teeth of man and the animals ; and in herbivora there is nor- 

 malh- excreted in the urine such large amounts of calcium salts 

 that by mere cooling they precipitate and the urine at time of 

 voidance may even be turbid from their presence (horse). Cal- 

 cium impregnates the matrix of bone and teeth with so much 

 uniformity of distribution that it is not apparent in definite masses, 

 being recognized only by the solidity of the structure and by 

 chemical analysis ; in the urine it separates as amorphous granular 

 and crystalline forms. 



The deposition of calcium salts in other parts than those men- 

 tioned is pathological and is known under the names calcification, 

 cretaceous iniiltration, petrification and incrustation. 



The basis for this deposition is probably to be sought in the 

 removal of the substances favoring the maintenance of the lime in 

 solution, as free carbonic acid, and the transformation of earthy 

 salts, which are soluble in water, into insoluble calcium compounds, 

 and, too, in increased supply of lime. Thus, pathologically, calcifica- 

 tion is apt to occur in dead or altered tissues in which free carbonic 

 acid exists in lowered amount and in which gaseous interchange 

 by the cells is essentially impaired, or may appear in secretions and 

 excretions where it leads to the formation of concretions. [Klotz 

 {Jour, of Exper. Med., 1905, vii, p. 633) has recently attempted 

 to explain pathological calcification in necrotic degenerative areas 



