M.
VAUGH
191
The applicability of the maximum pull to testing of
yokes seems even more definite. Presumably, ability
to pull a given load will be limited by one of two
things, the strength of the muscles or the unit
pressure under the yoke on the neck. The unit
pressure under the yoke as the result of a given draft
load will depend on the shape of the yoke and of the
animal's neck—on the fit of the yoke to the neck.
Tests of yoke to determine whether a difference
in the area of contact enables a bullock to pull more
or not seems to be one valid test of yokes. If it can
be determined that changes in the yoke do not
result in increased load pulled, it seems valid to
assume that the load pulled is limited by the muscular
power which can be applied by the animal. Since
we were not able to find any alternative test which
seemed to offer any advantage and since the results
to be secured by tests of maximum pulling ability
seemed theoretically valid, we feel justified in using
tests of maximum load pulled in both parts of the
scheme.
It is desirable, however, that tests be carried out to
determine the fraction of the maximum pull which can
be consistently pulled by working animals. While
as stated* above, one tenth of the live weight is
generally accepted as a suitable standard for horses,
there is little or no experimental evidence to sup-
port it, and the information we have seems to throw
doubt on it as a standard for bullocks. Desirable as
it may be to have the information, it is outside the
scope of this research problem.
As a preliminary step in the procedure, requests
were sent to the Director of Agriculture of each of the
provinces and of the larger Indian States known
to have organized Departments of Agriculture, asking
for dimensioned sketches of the typical yokes in use
in their respective areas. These requests brought
replies with drawings. These drawings were studied
to determine what variation there was among them,
and 15 types were selected as representing all the
differences likely to in any way affect the usefulness
of the yoke. Others appeared to be different only
in ornamentation or other similar unimportant
details. To these we added the 'Nagpuri' yoke in
use at the Institute and one made to dimensions
from the Almora hill district, making a total of 15
yokes selected for later testing. Two other yokes
were made and tested to check certain points,
making a total of 17 yokes actually tested. A
yoke was made to the design of Krishnamurty of
Madras Veterinary College. This is primarily a cart
yoke and it was found impracticable to test it with
the apparatus we were using. As it did not seem to
have any advantage likely to justify further attempts
to test it, it was excluded from the tests. Sketches
of these yokes are shown in Fig. 1 and Fig. 2.
EXPERIMENTAL DATA AND RESULTS
For the testing of the yokes, five pairs of bullocks
were selected from the work animals regularly in
use on the Institute Farm. A ploughman accustomed
to handling the bullocks was also selected from the
farm workmen and all tests were driven by the one
man. Whenever he was off duty for any reason,
testing was suspended and the staff was occupied
in other duties connected with the research. All
tests reported were done with the original five pairs
of bullocks. On the few occasions when any one
animal was indisposed for any reason, it was always
possible to carry on with another pair. No major
illness or injury to any of the test bullocks occurred
during the period of the tests.
The tests were carried out by Mr P. K. Bhargava
and Mr B. K. Mukerjee. Generally both were on
duty when tests were under way, and readings were
confirmed by both. On a few occasions, when it
was necessary for one of them to be absent, the other
carried on the testing alone. These occasions were
few.
Testing was started with yokes Nos. 1, 2, 3 and 4,
which were first ready. The procedure was to first
accustom the animals to the apparatus and to the
new yoke when a new yoke was taken in hand. Then
25 pulls with each pair on a yoke was made before
the next was taken in hand. When the full number of
tests on one group of yokes was completed with one
pair of bullocks, the other pairs were used in turn till
the whole group of yokes had been tested by all
five pairs. In the meantime, another group of yokes,
Nos. 5, 6, 7 and 8 were made ready and tests carried
out. In this way the first 15 yokes were tested a
total of 1,875 observations.
During these tests, certain difficulties were met.
The bullocks were totally unaccustomed to the parti-
cular type of work and to the slight noise the machine
made. They were only accustomed to the ordinary
field work of the farm and to the ordinary methods
of driving, and it was found difficult to control them
in any uniform manner. Sometimes they tended
to move quite fast and at other times they required
considerable urging. It was difficult to apply a
uniform degree of urging so that they put out the
same degree of effort every time. They tended to
learn that they could only go so far before the machine
stopped them and to be quite willing to stop when
they had reached what they estimated to be the
right place. This was partly overcome by driving
them in different directions and by the changing
of the testing from place to place. Some inter-
ruption was caused by rain on certain days and it
was necessary to suspend testing for some days
towards the end of the rains because the footing was
unfavourable when the ground became very wet and
covered with slime.
* Bulletin No. 240, Iowa State College of Agriculture and
Mechanical Arts, p. 219.
C 2