UDDER-ACTINOMYCOSIS 



107 



The fungus forms characteristic colonies in the animal 

 body. These structures are yellow or yellowish-brown, 

 round or irregularly shaped polygonally rounded bodies 

 from 0.1 to 2 mm. in diameter. The larger colonies are 

 always visible to the naked eye as yellow or yellowish-brown 

 points. 



AVith a magnification of 30 diameters they show a homo- 

 geneous wax-like appearance and a uniform or usually 

 slightly crenated margin (Fig. 25) . With a greater mag- 

 nification ( X 250) the margin presents a zone of radiating 

 club-shaped bodies (Fig. 26). 



On cut section and with greater magnification the col- 



FiG. 25. — Actinomyces 

 colonies in pus. Unstained 

 preparation in saline solu- 

 tion (X 30). 



Fig. 26. — Actinomyces 

 colonies in pus. Unstained 

 preparation in saline solu- 

 tion (X 250). 



FiQ. 27. — Actinomyces 

 colony. Cut section. Gram. 

 (X 300). Sporelike bodies 

 in the centre. 



onies present a core and a radiated finger-like margin. 

 The centre shows the little round spore-like bodies, and 

 outside, the margin shows the finger-like divisions and club- 

 shaped swollen filaments (Fig. 27). The most external 

 part of the margin formed by the club-shaped rays may 

 be deeply stained with eosin and picric acid. In this way 

 these stains are often of assistance in searching for the 

 colonies. 



The zone of club formations appears around the fila- 

 ments like a protective capsule. It only occurs on the 

 periphery and guards against the harmful protective in- 

 fluences of the animal host. The size of these clubs varies 



