AGf~ICULTURAL RESEARCH, PUSA.

266 PRACTICAL BACTERIOLOGY
diameter), delicate, semi-transparent, dewdrop-like
colonies, which tend to remain discrete-i.e. like
colonies of streptococci.
In bouillon--growth shows at first a uniform turbidity,
but later forms a granular deposit in the tube.
On hlood-agar-it is non-haemolytie, or only
partially lytlc, and the colonies procluce the same
greenish coloration as the" viridans " type of streptococcus.
'I'he colony is flat and smooth, and thc cdge
is often distinctly raised.
Cultures may show transformation of the colonies from the
typical stll()oth (t:i) type to the rmtgh (It) form; thifi variation
is nsso('iated with loss 01' ('apsu[c formation, absence of typespecificity
(vide infrll) and loss of virulence.
Bioche;wical Reactions.-Ferl1lents various Cal'hohydrates
(e.g. glucose, lactose, saccharose) and differs
from most strains of streptococci in its fermentation
of inulin. Hiss's scrum water, containing 1 pcr cent. of
peptone, is a convenient medium for these tests. The
medium used for testing the biochemical reactions of
the streptococcus also gives good results (vide p. 252).
It is sharply differentiated from the streptococci by its
solubility in bile. This test c:omists in ac1dillg 1 part
of sterile ox bile or 1 part of a sterilised 10 per cent.
solution of sodium taurocholate in normal saline to
10 parts of a bouillon culture. The test may also be
carried out by using a 10 per cent. solution of sodium
desoxycholate made distinctly alkaline to phenolphthalein,
0'1. e.c. being addcd to 1 c.C. of a broth
culture. This method gives very satisfactory results,
lysis occurring within fifteen minutes.
ViuVllity.-'l'he thermal death-point is al)out 52° C. The
ordinary laboratory cultures lose viability rapidly and require
to he subcultured nt short intervals (e.g. about fUUl·tecn days).
Cultures survive best in a semi-solid agar containing blood.
'l'he vitality and virulence of a strain can be maintained by
the method described below.
Expcl'itnental Inoculation. - Pathological material
containing pneumococci (e.g. pneulllonic sputum) or a