THli AC.CLUTIXATIOX Ti:ST. 423 



of typhoid fe\"ei", when it is simph' required to know whether 

 the ])atient's senini aggkitinates tlie typhoid bacillus, as an aid 

 to chnical diagnosis. In such a case a drop of the i)atient"s 

 serum is mixed with nine drops of an emulsion of typhoid bacilli, 

 and a dro]) of tlie mixture is then put on to a cover-slip, which 

 is then inverted over a well in an ordinary slide. The prepara- 

 tion is then incubated for an hour, and examined under tlie 

 microsco])e to see whether the bacilli have run into clumps. 



In the macroscojnc test first described one ha^ always to 

 l)ut up a contrt)l row of test-tubes, using in them the same 

 emulsion, but a serum whose agglutinating power on titre, as 

 it is calletl, is known. The emidsion of contagious abortion 

 bacilli must be from a strain which has been tested at frecjuent 

 intervals to see if the bacilli agglutinate well. Bacilli from the 

 same stock vary a good deal in sensitiveness to the action of 

 agglutinin. An organism which has been recently isolated does 

 not agglutinate as well as one which has been often subcultured, 

 l)ut, on the other hand, a very old culture loses its sensitiveness. 

 The sensitiveness can be reduced by growing the organism at 

 a temperature above the most suitable one or by growing it in 

 serum from an animal immunised against the disease whicli it 

 causes. 



In concluding the description of the agglutinins and the 

 agglutination test, it mav he stated that in i:)resent-dav research 

 an organism is always subjected to the test when its ultimate 

 proof as the cause of a particular disease is being attempted. 

 In the investigation of a new disease at the present day, should 

 .several organisnis of dilTerent sj)ecies be isolated from a case 

 of it. the test is particularly useful in deciding whether any one 

 entitled to regard that organism as a very possible cause of the 

 particular disease, and in conjunction with other tests the agglu- 

 onc particular species or organism, and not the others, one is 

 tination test ma\- help to establish the identit}' of the organism 

 of them is the causal agent. If the patient's serum agglutinate? 

 as the causal agent l)e\ond doubt. A few species of bacteria 

 do not cause the production of an}- measuralile amount of 

 agglutinin, therefore the al)sence of the agglutination in the 

 proof of an organism does not mean that it has no connection 

 with the disease in the ])atient whose serum was used in the 

 te<t. 



Betore showing liow the agglutination test may be applied 

 in the diagnosis and control of contagious abortion in cattle, a 

 shr)rt description of the disease must be given. The disease 

 itself is not fatal, and it is only because of the losses it causes 

 to dairy farmers and cattle breeders that it has become of so 

 much importance. The lesions which are i^resent in a cow 

 sufifering from the disease at the time when the calf is about 

 to be prematurely l)orn consist of an exudate between the 

 mucous membrane of tlie uterus and the outer envelope of the 



