G12 TRICHOMYCETES, ACTINOMYCETES, HYPHOMYCETES 
is absent unless blood or blood serumi is added, but even in enriched 
media the formation of clubbed forms is irregular. 
Actinomyces bovis stains by Gram's method, but the clubs are not 
colored . Eosin brings them out clearly. It has been held by Bostrom^ 
that the clubs are degenerative phenomena, but Wright'^ believes their 
chief function is a protective one, shielding the filaments from the 
harmful action of the bodv fluids and cells of the host. 
Fig. 88. — Actinomyces — club formation, semi-diagiammatic. 
Isolation and Culture.— The organism is anaerobic and appears to 
grow with moderate luxuriance in deep glucose-agar stab cultures. 
Material for inoculation is best obtained by crushing a granule between 
sterile' glass slides, or rubbing it on the inside of a sterile test-tube, 
after two or three preliminary washings in sterile salt solution to 
remove or diminish surface contamination. The finely macerated 
colony is distributed evenly in deep glucose-agar tubes and incubated 
at 37° C. After two to five days colonies appear scattered through 
the depths of the medium and are generally very numerous in a zone 
0.5 to 1 cm. below the surface. They do not ordinarily grow above 
this level. The deeply lying colonies increase in size until they 
measure 1 to 3 mm. in diameter at the end of a week's incubation. 
Microscopically these colonies consist of masses of radially arranged, 
branching filaments which exhibit a decided tendency to break up 
into short bacilloid or ovoid segments. A colony at this stage becomes 
a mass of compact short filaments and bacillary forms. Clubs are not 
seen imder these conditions unless blood or blood serum is added to 
the medium. 
In bouillon the organisms grow in dense white or gray masses of 
interwoven filaments which develop only at the bottom of the tube. 
Surface growth is never observed and turbidity practically never 
• Wright: Log. cit., p. 336. 
- Beitr. z. path. Anat. u. z. allg. Path., 1890, 9, 1. 
3 Lor. cit., p. 397. 
