AGf~ICULTURAL RESEARCH, PUSA.

300 PRACTICAL BACTERIOLOGY
The difference bctween the two types can be elicited
by injecting a rabbit intravenously with an emulsion
of 0'01-0'1 mgm. of dded bacilli (from a ,culture)
emulsified in saline. The bovine type produces an
acute generalised tuberculosis, and the animals usually
die within two months; in the case of the human type
the animals survive, or die only after two months,
with slight lesions confllled usually to lungs and (or)
kidney.
'l'he di:ITel'cntiation may also he brought out by injecting
10 mgm, 01' culture sulJcnt.aneously in the rahhit; the bovine
type leads to a general tuberculosis, Wllich j,s fatal usually
Within ten weeks, whereas the humall type produces only a
local lesion.
It is to be noted that strains which deviate in their
characters from the standard human and bovine types
may be met with. rrhus, strains isolated from lupus
are frequently of attenuated virulence for laboratory
animals (Griffith).
The bovine type of tubercle bacillus, in addition
to its association with tuberculosis of cattle, is the
commonest variety found in tubcrculosis of other
domesticated animals (e.g. sheep, pigs, h01'ses, cats).
OCCURRENCE OF TUBERCLE BACILLI IN HUMAN LESIONS
Both the human and bovine types are met with,
though the former is the more prevalent. '1'he latter
is infrequently found ill adults, but a. proportion of
tuberculous conditions in young subjects is due to this
type, particularly cases resulting from alimentary
infection by milk from tuberculous cows.
'rile pcrcentage frequency of thc bovine type of tubcrclc
bacillus, according to Gl'ilTIth, is as follows: tuberculosis
of ccrvical glands, 85'7 in England and 8·.1,.9 in Scotland in
children under five years, and 45'7 in Englnll(l and 73'0 in
Scotland at all ages; hones and ,ioints, 18 in England and
42'S in Suotlullcl; gcnito-urillnry SystCIll, 17' • .1. (England);
lungs, 0'8 in England anci a'S ill Suotland; meningitis, 30'1
(England); lupus, ,1,8'6 in Englanu and 53'S in Scotland.