204 BACTERIOLOGY. 



irregularly at its poles. The arrangement of these 

 nuclei appears in the sections sometimes as ovals, again 

 they are somewhat crescentic in their grouping. In the 

 tubercles from the human subject these large "giant- 

 cells," as they are called, are quite common. They are 

 much less frequent in the tubercular tissues from the 

 lower animals. 



Round about this 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 homogene- 

 ously. They vary in size and shape, and are seen to be 

 imbedded in a delicate network of fibrous-looking tissue. 



This fibrous-looking 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 " granulation tissue," 

 and consists of leucocytes, granulation cells, and the 

 fibrous remains of the part ; the irregularly oval, granu- 

 lar bodies which take up the staining are the nuclei of 

 these cells. The zone of granulation tissue surrounds 

 the whole of the tubercular process, and at its periphery 

 fades gradually into the healthy surrounding tissue or 

 fuses with a similar zone surrounding another tuber- 

 cular focus. This may be taken as the description of a 

 typical miliary tubercle. 



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. In this a large area 

 of tissue undergoes the same process of necrosis and 

 caseatiou as the centre of the miliary tubercle. In some 



