474 Veterinary Medicine. 



lymphoid cells in a fine fibrous stroma. Baumgarten and his; 

 followers claim that the larger epithelioid and giant cells result- 

 f rom the karyokinesis and proliferation, of the fixed tissue cells,, 

 epithelial and endothelial cells, and that the lymphoid cells which, 

 later (often after the eighth day in experimental cases) invade 

 the lesions, are alone the product of the migrating leucocytes.. 

 Metchnikoff, Yersin and others contend, on the other hand, that 

 epithelioid and giant cells are directly derived from the leucocytes- 

 and endothelial cells and like these are possessed of actively 

 phagocytic qualities. As the final outcome before caseous de- 

 generation, is the predominance of the small lymphoid cell, 

 it may well be questioned whether this is not the result of active 

 encrease in both kinds of cells, as appears to happen in many 

 other inflammations. For our present purpose it is well to note 

 the early characters : Centrally often a large (giant) cell with a 

 number of peripheral nuclei and at times, branching processes - 

 around this as a second zone epithelioid cells of large size, with 

 round or oval nuclei, and sometimes giant cells; outside this a. 

 third zone of small rounded lymphoid cells with large nuclei. 

 There is a delicate fibrous network between the cells, but no in- 

 dication of capillary blood vessels, the absence of which may 

 partly explain the constant tendency to degeneration, necrosis,, 

 and caseation. The tissue around the miliary tubercle is red and 

 congested. 



Caseation . A striking characteristic of tubercle is the occurrence 

 of coagulation necrosis, beginning in the centre of the specific 

 nodule as a whitish or pale softening and degeneration of the cell 

 elements and gradually extending toward the circumference. The 

 cells, and even the proximate tissue elements, die and disintegrate- 

 passing into a structureless, granular or hyaline debris, which has 

 been named from its supposed resemblance to old, ripe, soft 

 cheese. Baumgarten has observed that the small lymphoid cells- 

 are the first to degenerate, followed by the epithelioid and giant, 

 ones. 



While the formation of tubercle is at first a productive inflam- 

 mation of which the cell clusters and nodules are the result, yet 

 the tendency to necrosis, and caseation is so great that it must be 

 looked upon as one of its most prominent features, and is rarely 

 absent, whether the lesion exists in the connective tissue of the 



