THE HIGHER BACTERIA 969 



environment which is entirely free from oxygen, or at least contains 

 it only in small quantities. The method for isolation recommended 

 by Wright is, briefly, as follows: Pus is obtained, if possible, from 

 a closed lesion and washed in sterile water or broth. The granules 

 are then crushed between two sterile slides and examined for the 

 presence of filaments. If these are present in reasonable abundance, 

 the material is distributed in tubes of glucose agar, which are then 

 allowed to solidify. If these first cultivations show a large number 

 of contaminations, Wright recommends the preservation of other 

 washed granules in test tubes for several weeks, -in the hope that 

 contaminating microorganisms may thus be killed by drying before 

 the actinomyces lose their viability. 



If cultivation is successful colonies will appear, after two to four 

 days at 37.5 C., as minute white specks, which, in Wright's cultures, 

 appeared most abundantly within a zone situated 5 to 10 millimeters 

 below the surface of the medium. Above and below this zone they 

 are less numerous, indicating that a small amount of oxygen 

 furnishes the best cultural environment. Upon the surface of agar 

 slants, growth, if it takes place at all, is not luxuriant. 



In alkaline meat-infusion broth growth takes place in the form 

 of heavy, flocculent masses which appear at the bottom of the tubes. 

 Surface growth and clouding do not take place. 



Milk and potato have been used as culture media but are not 

 particularly favorable. 



Pathogenicity. As stated above, actinomycosis occurs spon- 

 taneously most frequently among cattle and human beings. It may 

 also occur in sheep, dogs, cats, and horses. Its locations of pre- 

 dilection are the various parts adjacent to the mouth and pharynx. 

 It occurs also, however, in the lungs, in the intestinal canal, and 

 upon the skin. When occurring in its most frequent location, the 

 lower jaw, the disease presents, at first, a hard nodular swelling 

 which later becomes soft because of central necrosis. It often in- 

 volves the bone, causing a rarefying osteitis. As the swellings break 

 down, sinuses are formed from which the granular pus is discharged. 

 The neighboring lymph nodes show painless, hard swellings. His- 

 tologically, about the filamentous knobs or granules, there is a 

 formation of epithelioid cells and a small round-cell infiltration. In 

 older cases there may be an encapsulation in connective tissue and 

 a calcification of the necrotic masses, leading to spontaneous cure. 

 As a rule, this process is extremely chronic. Infection in the lungs 



