10 BULLETIX 517, V. S. DEPARTMENT OF AGRICULTUEE. 



The disadvantages of work with artificially infected birds, due to 

 the large amounts of culture injected and to the severe reactions re- 

 sulting, were thoroughlj?^ realized, and work wdth naturally infected 

 birds was undertaken. 



FIELD TRIALS OF THE INTRADERMAL TEST. 



Through the courtes}^ of the Connecticut agricultural experiment 

 station, opportunit}^ Avas afforded to apply the intradermal test to 

 two flocks tested at the same time by Dr. L. F. Kettger by the agglu- 

 tination method. 



One flock of 231 birds injected on February 28, 1916, contained at 

 the time over 40 birds showing more or less evidence of swelling of 

 the wattles due to frostbite, while 6 others showed very slight swell- 

 ing attributed to the same cause. When examined 38 hours after 

 injection none was regarded as showing reaction to the intradermal 

 test. One bird gave a reaction to the agglutination test and was 

 killed by the owner before arrangements were made to retest by the 

 intradermal method. However, the owmer had made an autopsy and 

 reported that he regarded the bird as infected. 



In the second flock in w^hich work was done the Connecticut Agri- 

 cultural Experiment Station tested 50 birds in the regular routine 

 work of testing. Of these 1 reacted to the agglutination test and 

 failed to react to the intradermal test w^hen examined 46 hours after 

 injection. A number of birds showed slight abnormal conditions, 

 regarded at the time as due to frostbite, but noted in connection with 

 the problem of determining the least amount of swelling to be re- 

 garded as a significant intradermal reaction, under the conditions in 

 question. 



The bird that gave a positi^'e reaction to the agglutination test was 

 retested by both methods about a month later by Dr. Rettger. At 24 

 hours after injection the wattle was swollen to about 2.5 times normal 

 thickness, and when observed at 48 hours the swelling w^as 1.5 times 

 normal. An agglutination test made at the same time also gave posi- 

 tive results. It is probable that the failure of the intradermal test 

 when used the first time w^as due to some error in technique. Further, 

 it is the belief of the writers that readings should be taken at about 

 24 hours, and not as late as 36 and 48 hours, as in these trials. 



In the same flock the intradermal test alone was applied to about 

 100 birds, and those showing any enlargement of the wattle at 46 

 hours were tested by the agglutination method by Dr. Rettger. The 

 results yielded by both methods are given in Table VIII. The size 

 of the swelling following the intradermal injection is indicated as 

 nearly as possible by arranging them in order of decreasing size from 

 the top to the bottom of the list. Here, again, cognizance was taken 



