228 VETERINARY PATHOLOGY. 



salts in solution filtering into the tubercles; the liberated car- 

 bon-dioxide combines with the soluble lime salts forming insolu- 

 ble calcium carbonate which is deposited in the tissue thus pro- 

 ducing calcification. Enzymotic action is also present in local 

 areas of tissue, other than tubercular, that have recently become 

 necrotic, as inspissated pus, thrombi, infarcts, necrotic areas in 

 arteries, and there is also sufficient soluble lime salts present 

 to combine with the carl)on-dii )xide liberated Ijy the enzyms to 

 form insoluble calcium carljonate, thus necrotic tissue l:>ecomes 

 calcareous. 



Dense fibrous masses are frequentlv poorly nourished because 

 (if the (j1:)literated vessels and occasionalh' become calcareous. 

 Thus it is not rare to find calcareous centers in the dense fib- 

 rous tissue of fistulous withers. 



Improper Food. — Food or water containing excessive quanti- 

 ties of certain lime salts predispose to calculus formation and in 

 Slime instances to tlie deposition of lime salts in tissues as the 

 kidney and lung. 



Inhalation of air coutaiiiiiK/ lari/e quantities of lime or c!.:y dust 

 in suspension, results in their dep'isition in the alveoli of the 

 lung, and infiltration into the framework of the lung ])roducing 

 the condition known as chalicosis. Horses and mules worked 

 in and around cement plants, stone crushers, rock quarries, etc., 

 are aft'ected with pulmonary chalicosis and are more subject to 

 pulmonar^' diseases than animals not so aft'ected. 



There are probably some chemic substances, resident in the 

 body which when increased or diminished favor the deposition 

 of lime salts. Tt luav be that the chemic reactions of a tissue is 

 a factor of considerable moment in calcareous infiltration. 



Appearance. — Macroscopic. — Tissue affected with calcareous 

 infiltration is hard, granular and gritty. When palpated, it is 

 quite resistant and may be massive, but is more likely to be com- 

 posed of small calcareotts masses held together by variable quan- 

 tities of soft tissue. It is gritty when incised or sawed and in 

 some instances the tissue is so densely infiltrated that it is impos- 

 sible to either cut it with a knife or saw, a chisel being required 

 to break it asunder. Calcareous tissues are heavier than normal 

 tissues. Tissue mav be equally afl^ected throughout or the calcar- 

 eous material may be concentrated in small areas arranged con- 

 centrically around a central mass or in lines radiating from a cen- 

 tral point. The calcareous material mav appear in spherical 

 masses as in the tubercular lesions or in scales as in arteries 

 affected with athermatous degeneration. The air cells and bron- 

 chioles in the lungs of horses affected with chalicosis contain 



