and § Public Health Laboratory, PrestonB R U C E L L O S I S presents in three forms-acute brucellosis, chronic brucellosis following an acute attack and chronic brucellosis of insidious onset. Because the rate of isolation of Brucella abortus from blood or tissues is low, laboratory diagnosis of this disease is based mainly on the results of serological tests, the results of which depend on the clinical form and stage of the infection. The use of some of these tests in chronic brucellosis has already been discussed (Kerr, Coghlan, Payne and Robertson, 1966a and b).The variety of technical procedures employed at present leads to results that cannot be equated between laboratories. The purposes of this paper are to present details of these tests so that comparable results may be obtained and to indicate the way in which the results may be interpreted to help to determine the stage of the infection. The paper is presented in two parts; the first deals with a description of the tests and the second with their interpretation. There is also an appendix in which certain technical minutiae omitted from the main text may be referred to. The following tests are dealt with: (A) the standard agglutination test ; (B) the mercaptoethanol test (agglutination in the presence of 2-mercaptoethanol) ; (C) the anti-human globulin (Coombs) test (AHG test) for non-agglutinating antibodies ; (D) the complement fixation (CF) test. TECHNICAL PROCEDURESIn all cases Brucella abortus (BY. abortus) agglutinable suspensions are used for the tests, but in certain circumstances, to be discussed later, Brucella melitensis (Br. melitensis) suspensions are included. The standard agglutination test Mate vialsAntigen. Three different Br. abortus suspensions have been available to the authors for investigation. They are " Weybridge " standardised BY. abortus " agglutination concentrate", produced by the Veterinary Laboratories of the Ministry of Agriculture, Fisheries and Food, Weybridge, England; Br. abortus " concentrated 0 suspension " produced by the Standards Laboratory, Central Public Health Laboratory, London (PHLS); and " Wellcome " Br. abortus " agglutinable concentrated smpension " produced by Burroughs Wellcome and Co. These three suspensions differ in their cell concentrations, and since an inverse linear relation exists between the concentration of the bacterial cells and the

1. The normal agglutinin (n.a.) for Trichomonas foetus found in all normal adult cattle has a titre of 1:48 to 1:96. N.a. appears to be specific for T. foetus and cannot be absorbed by other flagellates such as T. vaginalis or even completely by the heterologous serological variety of T. foetus itself. The n.a. appears to be a native constituent of the serum and not to be induced by an exogenous antigen.2. The n.a. passes into the serum of the calf from the maternal colostrum during the first 24 hr. of life. The elimination of the passive n.a. and the development of the autogenous newly formed n.a. in the calf are traced. The passive n.a. disappeared from the 17th to the 55th day and the autogenous n.a. began to appear as a rule from the 35th to the 60th day and was fully established by the 63rd to the 113th day.3. The elimination of the maternal, induced antibody acquired passively from the colostrum took place logarithmically. The rate measured by the half-life ranged from 14 to 20 days, but in one animal which took a very large amount of colostrum it was 57 days.4. The intramuscular injection of T. foetus antigen into very young calves up to 4 weeks old induced no antibody. When the doses were relatively small the animal produced antibody to antigen given at a later period. When a very large amount was injected in this early period the subsequent capacity to respond to the same antigen but not to other antigens was seriously impaired.The personal encouragement of Prof. H. G. Lamont and the support afforded by the Ministry of Agriculture, Northern Ireland, are gratefully acknowledged.

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1. Antibody occurs in the uterus and can be withdrawn by irrigation. Intrauterine antibody results from the introduction of antibody into the lumen of the uterus.2. Neither free antibody nor the sensitization of the uterus has been produced by intramuscular injection of antigen, even when antibody has circulated in the bloodstream for periods from a few weeks to many months.3. Active sensitization of the uterus follows upon the repeated introduction of antigen into the uterus.4. It is concluded that antibody can be produced locally by some of the cells in the uterus when T. foetus antigen is present.5. The uterus of the cow can be sensitized passively in vivo by the instillation of bovine anti-trichomonas serum so that the instillation 6–10 days later of Trichomonas antigen will produce the characteristic local anaphylactic reaction.