374 ACTINOMYCES 



Other terms such as Streptothrix or Nocardia have been applied to organisms 

 of the Actinomyces group. Since the term Streptothrix was given by Corda in 

 1839 to a genus of fungi belonging to the Hyphomycetes, quite different from the 

 group that we are considering, this name is obviously inapplicable. The term 

 Nocardia was coined later than Actinomyces, and is likewise inapplicable. 



Habitat. — Many members of this group lead a saprophytic existence on grains 

 and grasses, and in water. As these substances are widely used as foods, it is not 

 unnatural that by their means Actinomyces often gains access to the alimentary 

 and respiratory tracts of man and other animals. They have been isolated chiefly 

 from man and cattle, and also from pigs, chickens, rabbits, dogs, elephants, 

 lizards, and oysters (Foulerton 1910). Most members live in the soil, where 

 they play an important part in the biological processes that are occurring there. 



There is at least one 



^, ^ species that appears to be 



N^ A< a strict parasite in man 



^ V -^r and animals. Numerous 



^r members are pathogenic 



for plants, causing such 



diseases as potato scab. 



Morphology. — On cul- 

 / ture media the morpho- 



^ logy is variable. In ordin- 



V ary film preparations the 



anaerobic Wolfi-Israel 

 type occurs chiefly as rods, 

 3-4 // long by 0-6 ^ broad, 

 which from their arrange- 

 ment, their clubbed ends, 

 ^fer and their irregular staining 



bear a resemblance to 

 certain members of the 

 corynebacteria ; careful 

 Fig. 58. — Actinomyces bovis X 1000. search, however, will 



From an agar slope culture, 14 days, 37° C. anaerobically. generally reveal a few 



definite filaments, some of 

 which may show true branching (Fig. 58). The aerobic type in young cultures 

 occurs chiefly as long unsegmented straight or wavy filaments, which show simple 

 or dichotomous branching (Fig. 59), and which not infrequently grow upwards 

 from the surface as aerial hyphse. Later these filaments undergo segmenta- 

 tion, and break up into rod forms of varying length and oval coccoid bodies, 

 which are usually referred to as spores. In some strains of the aerobic type 

 segmentation is visible within 24 hours ; in others it may not occur for 3 weeks 

 or more. On solid media the filaments are arranged in loose groups or in a 

 tangled mycelium, but in broth definite colonies occur consisting of a densely 

 matted central core of filaments and a peripheral zone in which the filaments are 

 more loosely disposed (Fig. 63). These colonies in liquid media are common to 

 both the aerobic and the anaerobic types. The rods and filaments may stain 

 evenly, but as a rule granular staining is evident. After growth for some time 

 in liquid media both the aerobic and the anaerobic types may show involution 



