14 BULLETIN 517, U. S. DEPARTMENT OF AGRICULTTJRE. 



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. 

 While some observations on birds in the field made during freezing 

 Aveather 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 prodvice a reaction. 

 Also limited complement-fixation tests on the blood serum of infected 

 fowls gave uncertain readings. 



SUMMARY AND CONCLUSIONS. 



A killed culture of Bacterium- pullorviTn grown for about a month 

 and held for several v/eeks before use and Avithout 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. jndlorum 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 w^attle 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. 



