650 Actinomycosis. 



of abundant fibrous tissue niaj' cause the destruction of the 

 actinomyces and thus bring about spontaneous recovery. 



Occasionally in loose connective tissue generally, especially 

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

 numbers of leucocytes from the surrounding vessels as a result 

 of the irritation produced by the parasite. Following this, 

 large areas of the tissue surrounding 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 

 AvalJ. 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 walls 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 liead 

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

 internal organs are only rarely affected. 



Fig. 102. Aitiiioiiiycotic Ulcer on the Uorsum of the Tongue (food cavity) in an Ox. 



Actinomycosis of the tongue frequently takes the form 

 of an ulcer situated immediately anteriorly to tlie 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 the tongue there 



