THE PATHOGENIC HIGHER BACTERIA 



539 



interwoven filaments which develop only at the bottom of the tube. 

 Surface growth is never observed and turbidity practically never 

 occurs. Freshly heated broth, in which the dissolved oxygen has 

 been driven off, appears to afford a somewhat more luxuriant growth, 

 particularly during the first few days' inoculation, but this precau- 

 tion is by no means absolutely necessary to obtain development. 

 Prolonged cultivation in broth frequently causes the organisms to 

 lose the discrete, mulberry-like colony; the growth becomes some- 

 what flocculent and viscid. Milk and other artificial media, aside 

 from agar and bouillon, are not favorable for the development of the 

 organisms. 



FIG. 83. Actinomyces mycelioid development, semi-diagrammatic. 



Actinomyces bovis does not grow at temperatures much below 37 

 C. Development ceases at room temperature. The resistance to 

 drying is considerable, fifty days being about the minimal time required 

 to prevent growth. In artificial media, however, the organism usually 

 becomes non-viable in a shorter period. The thermal death point is 

 about 62 C. for five minutes. Toward ordinary antiseptics, Actino- 

 myces is very resistant, but it is claimed that methylene blue is strongly 

 germicidal to it. 



Products of Growth. Neither toxins nor enzymes have been detected 

 in cultures of Actinomyces bovis. It is believed that toxins are not 

 produced. 



Pathogenesis. Animal and Human. Actinomycosis occurs as a 

 spontaneous infection both in cattle and in man ; much more commonly, 

 however, in the former. Other mammals horses, asses and sheep 

 are occasionally infected. The lesions belong to the group of the 

 infectious granulomata and the portal of entry of the organism is 



