14 BULLETIN 517^ U. S. DEPARTMENT OE AGEICULTUEE. 
observing a significant edema. The tests on birds in the laboratory 
and probably also those in the field indicate that 48 hours is too late, 
^^^lile some observations on birds in the field made during freezing 
T^'eather would indicate that slight swellings should not be con- 
sidered, yet the entire experience with birds in the laboratory indi- 
cates that even a trace may be indicative of a positive reaction. Some 
few cases would indicate that a 24-hour reading might give false 
results due to the inclusion of some cases in which the preliminary 
nonsignificant swelling had not quite subsided. At present, the 24- 
hour interval has given the best results, but the examination of a 
series of readings at 30 hours would be desirable. 
VARIOUS BIOLOGIC TESTS. 
During the course of these experiments several attempts were made 
to produce a reaction to the diagnostic agent by injection into the 
comb, but no satisfactory results were obtained. The ophthalmic, 
palpebral, and subcutaneous tests also failed to produce a reaction. 
Also limited complement-fixation tests on the blood serum of infected 
fowls gave uncertain readings. 
SUMMARY AND CONCLUSIONS. 
A killed culture of Bacferiurrb pullorinn grown for about a month 
and held for several weeks before use and without further treatment 
other than carbolizing, has given the most satisfactory results. 
It seems to be a fact that the edematous swelling resulting from 
the injection of this product into the wattle of a fowl, when observed 
at a proper time interval, is an indication of the presence of infection 
of B. indlorum in the fowl. 
Our experience to date with readings at various time intervals leads 
to the conclusion that the 24-hour interval has given the most accu- 
rate results. However, it seems desirable to test on a large number 
of birds the accuracy of readings made at a slightly longer interval. 
The weight of evidence indicates that any perceptible swelling of 
the wattle should be regarded as significant. A second intradermal 
test made at an interval of four days gave results varying but little 
from the first test. Others made at intervals up to two months ga^'e 
less accurate results the second time. Thus, there is no advantage in 
retesting. 
Of birds artificially infected with the disease and tested in the 
laboratory, in round numbers 90 per cent gave positive reactions; and 
in 6 per cent the test failed to indicate a reaction when lesions were 
present. In 3 per cent no reaction occurred and no lesions were 
present. 
