FREQUENCY OF NATURAL INFECTION 413 



are not stained uniformly, but they show unstained portions which 

 are known as vacuoles. Some of the filaments are broken up into 

 rod-like portions, others into round or oval granules. The latter are 

 spores. They do not have the staining properties of the true bacterial 

 spore, but are more resistant than the vegetative filaments. The 

 characteristic rosettes seen in natural infection are never seen in 

 artificial cultures. 



Resistance. Actinomyces cultures are quite resistant to drying out; 

 they are killed, according to Domec, at 60 C. in five minutes, but 

 the spores require 75 C. for five minutes before they are destroyed. 

 According to others the spores can resist drying out for six years 

 and are unaffected by 75 C. for fifteen minutes, but killed only by 

 80 C. acting for fifteen minutes. 



Animal Inoculation. On calves and small laboratory animals this 

 is, as a rule, not successful. Sometimes a local self-limiting process 

 occurs, but a progressing affection identical with the natural clinical 

 course of the disease has perhaps never been produced. 



Natural Infection. It is now generally accepted that the disease 

 is almost invariably transmitted to persons or susceptible animals 

 through the hulls of grain, straw, hay, splinters of wood, etc., which 

 are contaminated with the fungus and carry it deep down into the 

 tissues. Johne's early observation in regard to finding actinomyces- 

 bearing barley hulls in the tonsils of swine has already been referred 

 to. Since then numerous observers have succeeded in finding such 

 infected material in the tissues of actinomycotic lesions in man 

 and animals. Bostroem examined 32 cases of actinomycosis of the 

 upper or lower jaw in cattle, and he regularly found hulls deeply 

 wedged in between the teeth and the gums, or he found them still 

 deeper in the osseous granulations. These hulls were studded with 

 ray fungi. Bang showed that the ray fungus grows well on grains, 

 particularly on barley. Berestnew succeeded in finding ray fungi on 

 dry grasses, grains, and straw by introducing them into sand kept in 

 glass vessels in the incubator and moistening the vegetable parts with 

 sterile water. Under these conditions colonies of ray fungi devel- 

 oped on the material collected in the outside world. The mode of 

 transmission through infected grain has also been shown to be true of 

 man in whom it has been repeatedly demonstrated that the entrance 

 of hulls into the tissues of the mouth, the pharynx, the hands, etc., 

 has been followed directly by the development of actinomycotic 

 lesions. There is no convincing evidence of direct transmission 

 from one sick animal to another, and no case has ever been reported 

 to show contagion^ from cattle or other animals to man. 



Frequency of Natural Infection. In man actinomycosis is com- 

 paratively rare; in cattle it is very common and occurs among them 

 both sporadically and endemically, and occasionally as an epidemic. 

 In certain localities the fungus is evidently widespread and the 

 opportunities for infection are numerous. 



