AGf~ICULTURAL RESEARCH, PUSA.

4,04 PRACTICAL BACTERIOLOny
medium; older colonies become umbilicated and
assume a elry appearance.
In gelatin-slow liquefaction occurs.
No pathogenic effects have becn demonstrated by
experimental inoculation.
Anael'obic Type (Actinomyces bovis).-The optimulU
temperature is 37° C., and growth docs not occur at
temperatures much below the optimum.
On agar (under anaerobic conditions) colonies are
raised, grcyish-white, opaque discs which tend to
show a rosette form and are firmly adherent to the
medium.
A shake culture in a tubc of agar presents a char·
acteristic distribution of the colonies, which arc 1110st
numerous in a zone from 10-20 nun. bclow thc surface
-i.e. where there is only a trace of free oxygen present..
If the organism is grown in the fmIll of a stab
culture in agar, growth is also at an optimum in a.
sim.ilar zone. Though for all practical purposes this
organism is anaerobic, it shows a micro-aerophilic
character, a minute trace of oxygen being mol'e
favourable to growth than complete anaerobiosis.
By experimental inoculation of cattle and laboratory
animals (e.g. rabbits, guinea-pigs) circul1lscri.bcd
nodular 01' "tumour-like" granulomatous lesIOns
have been produced, in which colonies of the ol'ganisl11
are demonstrable.
OccuTrence.-Actillomycosis is an infective granuloma,
occurring mainly in cattle, sheep and pigs, and
occasionally in man. In human cases the lesions
usually show a suppurative tendcncy, and thc pus
contains colonies of the parasitc in the form of small
round granules about the size of a pin-head, which
are occasionally of a bright yellow colour (like grains
of sulphur). These granules can be recognised by the
naked eye if the pus is examined in the form of a thin
layer on a slide. The commonest avenue of infection
in man is through the mucosa of the mouth or throat.
The mode of infection is often doubtful, and it may be
impm;sible to trace the source. 'fhc initial infectivity