VARIETIES OF ACTINOMYCES 



325 



anaerobe and in ceasing to grow at a temperature a little below 

 that of the body. Under ordinary aerobic conditions either no 

 growth occurs or it is of a very slight character. On the surface 

 of agar under anaerobic conditions the organism produces dense 

 rounded colonies of greyish-white colour, which sometimes 

 assume a rosette form. A somewhat curious feature of growth 

 is described by Wright, namely, that in a shake culture in 

 glucose agar the colonies are most numerous and form a dense 

 zone about half an inch from the surface of the medium, that 

 is, at a level where there 

 is presumably a mere 

 trace of oxygen obtain- 

 able (Fig. 96). In 

 bouillon, growth takes 

 place at the bottom of 

 the medium in rounded 

 masses which afterwards 

 undergo disintegration. 

 Wright found when the 

 organism was grown in 

 the presence of serum or 

 other animal fluids, that 

 the formation of true 

 clubs occurred at the 

 extremity of some of 

 the filaments (Fig. 97). 

 From the conditions 

 under which growth 

 occurs, he is inclined to 

 regard it as a true para- 

 site, and doubts whether it can have a saprophytic existence out- 

 side the body, e.g. on grain. He is also of opinion that all cases 

 of true actinomycosis, i.e. cases where colonies visible to the 

 naked eye are present, are probably produced by one species, and 

 that the aerobic organisms obtained by Bostrom and others are 

 probably accidental contaminations. It is quite evident that 

 further investigations are required in the light of the results 

 detailed. Certainly the parasite in many cases of actinomycosis 

 in the human subject does not grow on ordinary media under 

 aerobic conditions as Bostrom's organism does. 



Varieties of Actinomyces and Allied Forms. It is probable that in 

 the cases of the disease described in the human subject there is more than 

 one variety or species of parasite belonging to the same group. Gasperini 

 has described several varieties of actinomyces boris according to the colour 



95. Actinomyces, from a culture on 

 glycerin agar, snowing the branching of 

 the filaments. See also Plate III., Fig. 10. 

 Stained with fuchsin. x 1000. 



