BACTERIUM TUBERCULOSIS 407 



ridges, the remains of tissues not yet completely destroyed. 

 Around the periphery of this area may sometimes be noticed 

 large multinucleated cells, the nuclei of which are arranged 

 about the periphery of the cell or grouped irregularly at 

 its poles. The arrangement of these nuclei as observed 

 in sections is usually oval, or somewhat crescentic. In 

 tubercles from the human subject these large "giant-cells," 

 as they are called, are quite common. They are much less 

 frequent in tubercular tissues from lower animals. 



Round about the central focus of necrosis is seen a more 

 or less broad zone of closely packed small round and oval 

 bodies, which stain readily but not homogeneously. They 

 vary in size and shape, and are seen to be imbedded in a 

 delicate network of fibrinous-looking tissue. This fibrin- 

 like network in which these bodies lie, and which is a 

 common accompaniment of giant-cell formation, is in part 

 composed of fibrin, but is in the main, most probably, the 

 remains of the interstitial fibrous tissue of the part. This 

 zone of which we are speaking is the zone of so-called " granu- 

 lation-tissue," and consists of leukocytes, granulation-cells, 

 fibrin, and the fibrous remains of the organ; the irregularly 

 oval, granular bodies which take up the stain are the nuclei 

 of these cells. The zone of granulation-tissue surrounds 

 the whole of the tuberculous process, and at its periphery 

 may fade gradually into the healthy surrounding tissues or 

 be sharply outlined or may fuse with a similar zone sur- 

 rounding another tubercular focus. 



Diffuse Caseation. — ^The diffuse caseation, as said, plays 

 a more important role in the tuberculous lesion, both in the 

 human and experimental forms, than does the formation 

 of miliary tubercles. Here a large area of tissue undergoes 

 the same process of necrosis and caseation as the centre of 



