^ MASTITIS OF THE COW 



are taken up by the leucocytes in the blood, in wounds or 

 in the milk and carried into the lymph spaces of the stroma, 

 where the leucocytes are finally killed by the bacilli con- 

 tained within them. 



Primary Lesion and Inflammation. — Around these 

 necrotic cells which constitute the primary lesion, a number 

 of cells are attracted, in the process of inflammation, and 

 around these a layer of new connective tissue forms. This 

 structure is the primary tubercle. 



By progressive necrosis a figure called a giant cell is 

 formed in the centre. It is this round 

 or oval necrotic focus which presents 

 a zone of cell nuclei upon its external 

 border which are not destroyed by the 

 organism within its structure. The 

 necrotic focus thus resembles a large 

 cell with many nuclei, giving rise to 

 Fig. 23— Tuberculosis of the uamc giaut ccU (Fig. 23). The 



the udder. Stroma-infection . ii>-| 'ii-ji ii t 



(interstitial mastitis]. Primary orffamsms multiDly witlun thc tubercle 



cell necrosis and two giant cells "-^ . ■*■ "^ 



in the intralobular connective VCrV SlOWlV. 



tissue with corresponding in- J *' * i • i 



cytTanrw^u'^ofcoiC^iv; [H. F. Smyth, m his work on 

 deronstrIt"dTi%h:"aJerTf tissue cultuTC, has shown that tissue 

 necrosis with bacterial stams. jnoculatcd with tubcrclc bacilH and 



grown in vitro will form giant cells by fusion of epithelioi- 

 dal cells. The giant cells are forty or fifty times larger than 

 epithelioidal cells. Giant cells may be seen anywhere in a 

 tubercle, which usually presents a centre of cheesy necrosis 

 surrounded by a zone of epithehoidal cells, outside of which 

 is a zone of lymphocytes, which is later surrounded by a 

 layer of connective tissue.] 



Distribution. — The infection manifests a great ten- 

 dency to spread. A few bacilli in the primary tubercle 

 may be picked up by leucocytes and be carried further into 

 the stroma in the direction of the lymph stream where these 

 leucocytes may be destroyed by the organisms and daughter 



