650 



Actiuuuij^cosis. 



of abundant fibrinous tissue may cause the destruction of the 

 actinomyces and tlius bring about spontaneous recovery. 



Occasionally in loose connective tissue generally, especiallj^ 

 in swine, but also in man, there occurs emigration of large 

 numbers of leucocytes from the surrounding vessels as a result 

 of the irritation jDroduced by the parasite. Following this, 

 large areas of the tissue surrouncling the nodules undergo 

 purulent softening, become confluent with other similar areas 

 and thus produce large abscesses or fistulae which are always 

 surrounded by a thick and usually very firm connective tissue 

 wall. Occasionally the suppurating process is induced by 

 pyogenic bacteria which are met with most frequently in the 

 pus of the larger abscesses. 



The mycelium of the parasite may penetrate the cells of 

 the blood vessels and be transported to other regions of the 

 body, thus giving rise to the development of metastatic tumors 

 or abscesses such as are observed quite frequently in spongy 

 bones, but also in the brain and other organs. 



Anatomical Changes. The seat and character of the 

 anatomical changes vary with the species of animal. 



In cattle the tongue is most frequently affected, the maxillae 

 coming second; tumors of the skin in the region of the head 

 and neck as well as larynx are also quite common, Avhile the 

 internal organs are onlv rarelv affected. 



Fig. 102. Actinomycotic Ulcer on the Dorsum of tlie Tongue (food cavity) in an Ox. 



Actinomycosis of the tongue frequentl}^ takes the form 

 of an ulcer situated immediately anteriorly to the dorsal promi- 

 nence of the tongue (so called "food cavity"). In this con- 

 dition there are one or more ovoid lesions, or transverse bands, 

 consisting of loss of tissue substance; the bases of these lesions 

 are surrounded by raised borders and are covered by numerous 

 small depressions with ragged outlines. Hairs, or masses of 

 vegetable fibers project from the depths of these depressions, 

 sometimes in such quantities that they hide the entire lesion 

 from view (Fig. 102). Thus in a section of tlie tongue there 



