362 THE INDIAN JOURNAL OF VETERINARY SCIENCE AND ANIMAL HUSBANDRY [III, IV.

of a more suitable subject at the time, had to be fed upon dogs showing only
" rare " or " very rare " parasites.

As has been mentioned earlier in this note, the infectivity of the nymphs and
adults derived from one or more of the six lots of larvae was tested upon five dogs.
The results of these tests are summarized in the following Table :—

Dog
No.

Number of ticks
used

Number
of
ticks
recover-
ed

Duration
of
feed

Number
of days
dog kept
under
observation

Result

Incuba-
tion
period

Number
of days
parasites
seen in
blood

Remarks

194

300-400 nymphs
derived from
Lot C.

*About
100.

6 days

56 days

+

29 days

9 days

*Collar found
damaged
and cloth-
cover sli-
ghtly dis-
lodged.
Dog discon-
tinued.

236

About 200
nymphs derived
from Lot C

All .

6 „

73 „

+

30 „

24 „

Dog discon-
tinued.

248

About 100
nymphs derived
from lots fed
on both Dog
No. 239 and
Dog No. 240.

All .

6 „

89 „

+

28 „

18 „

Dog discon-
tinued.

34

About 100
adults derived
from mixed
lots as above.

All .

8 „

31 „

..

..

..

Died of sus-
pected dis-
temper.

29

About 90 adults
derived from
mixed lots as
above.

74

10 „

11 „

..

..

..

Died of pneu-
monia.

The incubation period shown in the foregoing table against each of the three
dogs that developed the infection represents the interval between the date on which
the ticks were placed upon the host and the first appearance of the parasites in
the circulating blood. It is noteworthy that this period was more or less constant
in the three animals, for this is a strong confirmatory evidence that the animals
actually developed the infection as a result of being bitten by the ticks and pre-
cludes the possibility of natural infection or resuscitation of dormant parasites.

It has already been remarked that an elevation in body temperature has not
been found to be a reliable indication of the development of artificial P. gibsoni