2o6 



ACTINOMYCOSIS 



Fig. 44. 77?^' ray fungus. 



§ 163. Etiology. Actinomyco- 

 sis is produced by a fungus — Clado- 

 thrix adviomyces commonly known 

 as the " ray fungus." The disease is 

 the result of its multiplying in the tis- 

 sues and not from the elaboration of a 

 toxin. The fungus appears in minute, 

 yellowish granules in the lesions. 

 When examined microscopically, these 

 granules are found to be made up of 

 rosettes varjnng in size from 10 to 

 200// in diameter. The average size 

 ranging from 30 to 40/<. This fungus can be cultivated on 

 artificial media. It stains somewhat feebly with the aniline 

 dyes. 



The rosettes are composed of a number of club-shaped struct- 

 ures (rays), radiating from the central mass which is composed 

 of the mycelial part of the fungus. The club-shaped bodies 

 vary in size but usually they are from i to lOyu long. The 

 rays are connected with the central portion by fine thread-like 

 structures which are not readily demonstrated. In tearing or 

 crushing the rosette, tlie clubs break off at or near their junc- 

 tion with the mycelial threads. Some investigators have men- 

 tioned a polymorphous form of actinomyces in which coccoid 

 and rod-shaped structures are found. These are doubtless the 

 ends of the clubs which first appear in focusing on a rosette. 



The mycelial threads are wider in some portions than in 

 others. In the narrowest places the walls seem to touch each 

 other. Whether this irregularity is natural or the result of 

 twisting the mycelial thread is not determined. The my- 

 celium is much more difficult to stain than the clubs. In some 

 cases it seems to branch. The filaments can rarely be seen in 

 the rosettes as they occur in the suppurating lesions. 



The natural habitat of this fungus is said to be on certain 

 plants. According to Brazzola, they vegetate on the grasses 

 chiefly on Hordeum imirimirn. He di.scovered quantities of 

 the fungi between the vegetable fibres of barley which were 

 imbedded in the gums of animals. Johne, Plana, Bostroem and 



