60 PATHOLOGY. 



are always tubercular is erroneous. In themselves, they merely 

 indicate that the growth has undergone a fatty metamorphosis, 

 but they do not furnish any evidence of any one particular form 

 of growth. As a result of pleuro-pneumonia, they merely indicate 

 that the exudate has undergone this form of metamorphosis, not 

 that there has been a tubercular growth. At a subsequent period 

 caseous material may be either calcified, or may become softened, 

 absorbed, tainting the blood-mass, or give rise to the formation 

 of tubercule-like tumours. 



CALCAEEOUS DEGENEEATION. 



Calcareous degeneration or calcification is an advanced stage 

 of caseation, and is chiefly found to take place in masses of 

 caseous material which are enclosed, and isolated from the influ- 

 ence of the external air, and it is a sure evidence that the growth, 

 whatever may be its nature, has been existent for some length of 

 time. Eokitansky considers the earthy materials not so much as 

 new deposits, but as precipitations of salts, principally consisting 

 of the phosphate of lime and magnesia, and carbonate of lime, 

 from their natural combinations with pre-existent animal matters. 



Calcareous degeneration does not always depend upon a pre- 

 viously fatty degenerate state of a part, although it often results 

 from such. It may occur under two opposite conditions, 

 namely, when there is an absolute increase of earthy matters 

 in the blood, and the excess deposited in the tissues ; and 

 wdien there is no such increase, the deposition of earthy salts 

 which then takes place being consequent upon some alteration 

 in the tissue itself. The former condition is oftener met with 

 in man than in the lower animals, and results from extensive 

 caries and other degenerative bone diseases, where the lime salts 

 are removed from the bones into the blood, and deposited in 

 other tissues. 



In such cases, the calcification affects many organs simul- 

 taneously, and it is not an uncommon thing to find the lungs, 

 kidneys, stomach, intestines, Hver, and even the dura mater, 

 infiltrated with lime salts. Again, it is found in man that 

 chronic disease of the kidneys leads to calcification of several 

 organs. This is due to the fact that the lime salts, which ought 

 to have been excreted by the kidneys, accumulate in the blood 



