424 THE AGGLL'TI.NATION TEST. 



foetus, which exudate is thick and creamy in consistence, varying 

 in colour from whitish yellow to brown. The cotyledons of 

 the foetal envelopes also show alterations, and generally appear 

 yellow and necrotic. These lesions are due to a chronic 

 catarrhal inflammation of the uterus set up by infection with 

 the organism which causes the disease. 'i'he foetus itself shows 

 very few lesions, and may on opening show inflammation of the 

 intestines or a lot of fluid in the abdominal and thoracic cavities. 

 A cow may become infected either by being served by a bull 

 which has become infected from a cow which has recently 

 aborted, or by taking in the organism with food which has got 

 contaminated with the discharges from a cow with the disease. 

 It was found that the serum of an infected cow agglutinated 

 the bacillus which is known to be the causal agent of the disease. 

 The possession of a means of controlling the disease is of the 

 utmost importance when it comes to be considered that such a 

 disease, if allowed to spread, will cause enormous losses to the 

 cattle breeder. In a single herd 80 per cent, of the cows may 

 prematurely calve, and as the calf is nearly always dead, and if 

 not, dies within a few days of birth, the loss can be understood, 

 as, in addition to the loss of the calves, the cows either give no 

 milk or very little. Abortion may occur at any time from the 

 sixth week of gestation to ,the eighth month. The calf may 

 even be born at the right time and die in a few days, being too 

 weak and sickly to live. 



In using the agglutination test as a means of controlling 

 the disease in a herd of cattle, it should be carried out in a very 

 systematic manner. On the suspicion of the presence of con- 

 tagious abortion in a herd being aroused, as it usually is, by the 

 occurrence of several abortions without any apparent reasons, 

 the serum of every animal, including the Ijull or bulls, should 

 be subjected to the test. As previously stated in the description 

 of the macroscopic method of doing the test, all sera which 

 agglutinate in a dilution of t :ioo or over should be considered 

 as being from an infected animal, though agglutination at the 

 1 :50 dilution raises suspicion in an infected herd. The sera 

 of cows which have actually al)orted usually agglutinate in dilu- 

 tions of an3'thing from i :200 to i :2000, or even higher. Those 

 animals which have given positive results should be isolated from 

 the non-infected ones, and the latter should again be tested after 

 the lapse of about a month, as it has been found that animals 

 very recently infected may not give a positive reaction to the 

 agglutination test, and it has been shown that a cow infected by 

 the mouth artificially will not give a positive reaction for at least 

 two weeks. In a case brought to our notice at the Laboratorv. 

 Onderstepoort, a cow was tested and gave an agglutination titre 

 of I 125, which would would be considered negative. The cow 

 aborted three weeks later, and at the date of al)ortion the serum 

 agglutinated in a dilution of i :200, which is a distinctly positive 

 reaction. The agglutination test will not do more than tell 



