BUEEAU OF ANIMAL INDUSTRY. 117 



transmission of this ameba to human beings through such sources 

 must be given cognizance. 



RABIES. 



The examination for rabies included many suspected cases from 

 Maryland, Virginia, and Kentucky, as well as the District of Colum- 

 bia. One hundred and thirty-five suspected cases were received for 

 laboratory diagnosis. The diagnosis was positive for 54 dogs, 7 cats, 

 4 cattle, 1 horse, and 1 mule, a total of 67 positive cases. In three of 

 the cases the material was so decomposed that no diagnosis was pos- 

 sible. In every instance where a person was bitten, animal inocula- 

 tion was resorted to when the microscopic findings were negative. 



Experiments conducted on a limited number of animals, including 

 dogs, sheep, and calves, with a view to determining the immunizing 

 power of rabies vaccine prepared after the Harris method, and of 

 dilutions of fresh fixed virus, have yielded some promising results. 

 This work, however, has not as yet afforded sufficient data on which 

 to base definite conclusions. 



TESTS FOR TUBERCULOSIS. 



In the testing of dairy cattle in various sections of the country with 

 tuberculin by means of subcutaneous injections, among the large 

 number of reactors there were 83 cattle that had apparently reacted 

 to the test and which were slaughtered under Government super- 

 vision but in which at the time of inspection no visible lesions of 

 tuberculosis could be demonstrated. Lymph glands from these cattle 

 were forwarded to the pathological laboratory, where they were first 

 tested microscopically, and if no tubercle bacilli were detected by this 

 procedure the glands were further tested by animal inoculation. As 

 a result 36 of the uncertain cases proved to be tuberculosis, while in 

 47 no evidence of tubercle bacilli was discovered. 



The intradermal palpebral method of applying tuberculin has 

 been giving excellent results in recent tests, and it has been suggested 

 that its use in retesting cattle that have given an uncertain reaction to 

 the subcutaneous injection of tuberculin might prevent the unneces- 

 sary slaughter of animals that are not visibly affected with tuber- 

 culosis. In this method the same technique is followed as in making 

 intradermal injections into one of the subcaudal folds, except that 

 the needle is inserted into the lower eyelid, at a point near its middle, 

 longitudinally, and about half an inch from its margin. Bureau 

 tuberculin, concentrated to 50 per cent of its original volume, was 

 selected as the best form of tuberculin for intrapalpebral use. One- 

 fifth to one-fourth of a cubic centimeter constitutes a suitable dose. 

 A reaction is manifested by a swelling of the lid which becomes very 

 apparent, so that the results of the test may be read from a distance. 

 As the reaction is produced automatically, no errors need be made in 

 interpreting results. 



Extensive investigations have been made into the reliability and 

 practicability of the complement-fixation test in the diagnosis of 

 tuberculosis. Eight hundred and sixteen samples of blood from 

 cattle were examined, most of them coming from animals that were 

 afterwards slaughtered under Federal supervision. Out of 320 nega- 

 tive sera, a total of only 279 (85.9 per cent) proved distinctly negative 



