2l6 BACTERIOLOGY. 



occurring in animals * and occasionally in man.t 

 It is caused by a parasite known as Actinomyces, 

 or the " ray-fungus." The parasite appears in the 

 form of a rosette of pyriform or club-shaped ele- 

 ments (Plate XXIX., Fig. i). The little masses are 

 colourless, pure white, or of a yellowish or yellowish- 

 green tinge, and visible to the naked eye. 



The fungus is believed to effect an entrance to 

 the animal by the mouth, being taken in with the 

 food, possibly through the medium of a wound of 

 the gum or a carious tooth. In whatever manner 

 it has gained access to the living organism, it sets 

 up inflammation in its neighbourhood, resulting in 

 the formation of a neoplasm, composed chiefly of 

 round cells, resembling a tuberculous nodule. 

 The nodules may break down and suppurate, or 

 may go on increasing in size. Fibrous tissue develops 

 between the nodules, and large tumours eventually 

 result containing purulent cavities and excavations. 

 In the slimy detritus the little pale-yellow grains 

 of fungus can be detected. In cattle the lower 

 jaw is usually anected, and then the upper jaw 

 and neighbouring parts. The organism may also 

 occur in nodular tumours in the lung, subcutaneous 

 and intermuscular tissue. It is the cause of 

 " wooden tongue," and also of diseases which have 

 been variously described before their true nature 



* Bellinger, Centralbl.f. Med. Wiss. 1877. 



t Israel Virchow's Archiv, vols. 74 78. Pontick, Die Actino- 

 mycose des Menschen, 1882 ; and Beitr z. Kenntn. der Actino- 

 mycose des Menschen, 1885; Lancet, May 2nd, 1885. 



