TUBERCULOSIS. 441 



In the first case, the tubercle is transformed into a semi-trans- 

 parent or white, consistent, cartilage-like mass (the fibrous tuber- 

 cle of Virchow), which must be regarded as dense callous con- 

 nective tissue 5 or the nodule changes into a firm, dark, pigmented, 

 homogeneous, sometimes stratified, mass that is, it becomes 

 horny or obsolete. These hard nodules, attaining sometimes the 

 size of a sugar-pea, are often found scattered in the lungs. 



If, on the contrary, the disintegration of the tissue has once 

 commenced, the crumbling mass becomes a foreign body, both as 

 regards the surrounding tissue and the whole organism. Here, 

 as around every foreign body, inflammation sets in, and the 

 tissue around it is transformed into a firm connective-tissue cap- 

 sule, of varying diameter. The encysted product of tubercle 

 becomes a viscid, fatty, sometimes pigmented, paste $ or lime- 

 salts are deposited in it, which results in its being transformed 

 into a dry, cement-like mass. Finally, it becomes calcified, and 

 is termed a calcareous concretion. 



The tissue in the neighborhood of the diseased focus behaves 

 differently, according to whether originally only discrete or con- 

 glomerated, and closely lying foci were present. The surround- 

 ings of a horny nodule are found to be lung-tissue, which is 

 radiatingly contracted, but otherwise normal, and from which 

 the hard mass can be easily dug out. The structures in the 

 neighborhood of a callous capsule, on the contrary, are firmly 

 concreted with it, so that the capsule cannot be separated from 

 the inclosing tissue. 



If from the very beginning, in a circumscribed district of 

 lung-tissue, numerous nodules and infiltrations are present, and 

 the lung- tissue itself is in the condition of a chronic inflamma- 

 tion, the transformation into a hard, consistent callosity takes 

 place, more or less extensively, usually in the apices of the lungs. 

 The .tissue is indurated, and, as it is almost constantly provided 

 with an abundant supply of dark pigment, the callosity appears 

 of a slate-color, or even black. This is the pigmentary induration 

 of Virchow, the cirrhosis of Corrigan and Buhl. 



In the indurated lung-tissue are found all the before-men- 

 tioned methods by which tubercle is healed viz. : the white, 

 almost cartilaginous, nodule, the size of a hemp-seed ; the gray 

 or black node of a concentric striation ; the cement-like or cal- 

 cified mass, directly imbedded in the callosity. 



Observation, therefore, teaches that a genetic separation of the 

 tuberculous nodule from the tuberculous infiltration is not admis- 



