Pathogenesis 809 



which it is carefully introduced through a small opening 

 made under aseptic precautions. In the eggs long, 

 branched mycelial threads quite unlike the bacillary forms 

 that grow upon agar-agar are formed. 



The characteristic rosettes so constantly found in the tis- 

 sues are never seen in artificial cultures. 



Virulence. When the actinomyces is grown upon artifi- 

 cial media the virulence is retained for a considerable time. 



Pathogenesis. Actinomycosis is almost peculiar to bo- 

 vine animals, but sometimes occurs in hogs, horses, and 

 other animals, and rarely in human beings. The disease 

 can with difficulty be inoculated into experiment animals, 

 the introduced fungi either becoming absorbed or encap- 

 sulated by connective tissue and not growing. In the 

 abdominal cavities of rabbits the peritoneum, mesentery, and 

 omentum show typical nodules containing the actinomyces 

 rays in cases of successful inoculation. 



Mode of Infection. The manner by which the organ- 

 ism enters the body is not positively known. In some cases 

 it may be by direct inoculation with infectious pus, but 

 there is some reason to believe that the organism occurs in 

 nature as a saprophyte, or as an epiphyte upon the hulls 

 of certain grains, especially barley. Woodhead has recorded 

 a case where a primary mediastinal actinomycosis in the 

 human subject was apparently traced to perforation of the 

 posterior pharyngeal wall by a barley spikelet accidentally 

 swallowed by the patient. 



Cases of actinomycosis are fortunately somewhat rare in 

 human medicine, and do not always occur in those brought in 

 contact with the lower animals. The fungi may enter the or- 

 ganism through the mouth and pharynx, through the respira- 

 tory tract, through the digestive tract, or through wounds. 



The invasion has been known to take place at the roots 

 of carious teeth, and is more liable to occur in the lower 

 than in the upper jaw. Israel reported a case in which 

 the primary lesion seemed to occur external to the bone 

 of the lower jaw, as a tumor about the size of a cherry, 

 with an external opening. Two cases of the disease 

 observed by Murphy, of Chicago, began with toothache and 

 swelling of the jaw. A few cases of dermal infection are 

 recorded. Elsching * has seen a case in which calcified 

 actinomyces grains were observed in the tear duct. 

 * "Centralbl. f. Bakt. u. Parasitenk.," xvm, p. 7. 



