1 24 Immunity 



agglutinative serum when exposed to a temperature of 65C. 

 loses the agglutinophores, and no longer clumps the bacteria, though 

 it retains the haptophores, and when brought into contact with the 

 bacteria combines with them, producing no agglutination, but pre- 

 venting the action of unheated agglutinogenic serum. 



Buxton and Vaughan* found that bacteria differ both in their 

 agglutinogenic powers and their agglutinability, both of which must 

 be taken into account in studying the subject. 



Theobald Smithf has shown that there are two kinds of agglutinins, 

 one of which acts upon the bacteria directly, the other through 

 the flagella. The occurrence of these two bodies explains some of 

 the incompatible results of previous experiments. 



The reaction is one of the most delicate known to us for the 

 identification of bacteria. It is so specific that, in the case of many 

 organisms, it is even possible to tell from what original source they 

 may have come, and always to tell to what variety they belong. 

 It is, moreover, a comparatively simple method that can be used by 

 physicians with little technical skill. The various serums necessary 

 can be obtained from the large public and commercial laboratories 

 where animals immunized against various cultures can always be 

 kept on hand and periodically bled. The serums, sealed in small 

 tubes, can be kept an almost unlimited length of time and shipped 

 to any distance ready for use when opened and diluted. 



There is no uniform technic by which to apply the test. Scarcely 

 any two laboratories employ the same method, but the results are 

 uniform and the method to be employed, provided it is free from 

 error, is that found most convenient to the individual operator. 



The agglutination test now subserves two important functions: 

 i, the diagnosis of any infectious disease, provided the infecting or- 

 ganism be at hand; 2, the recognition of any micro-organism, provided 

 specific serum be at hand. 



Technic of Agglutination Tests 



If possible, a culture of the micro-organism, grown upon agar-agar, is to be 

 selected for the purpose. A good-sized platinum loopful of the culture is taken 

 up and distributed as uniformly as possible throughout a few cubic centimeters 

 of distilled water. This is best done by placing the water in a test-tube and then 

 rubbing the culture upon the glass just above the level of the fluid, until it is 

 thoroughly emulsified, permitting it to enter the water little by little and, finally, 

 washing it all down into the fluid. This gives a distinctly cloudy fluid, too con- 

 centrated to use. Of this one adds enough to each of a series of watch-glasses 

 or test-tubes, each containing an equal volume of distilled water (say 2 cc.), 

 to make the fluid opalescent by reflected light though transparent by trans- 

 mitted light. The same quantity should be added to each, so that they form 

 a uniform series. The patient's blood or serum is next diluted and added so 

 that the watch-glasses or tubes receive a i : 10, i : 20, i : 30, i : 40, i : 50, i : 60, i : 80, 

 1:100, 1:150, 1:200, 1:300, or a laboratory serum of high agglutinative value, 

 1:1000, 1:2000, 1:5000, i : 10,000, 1:50,000, and 1:100,000. 



If watch-glasses are used, they are stood upon a black surface, covered, 



* "Jour. Med. Research," July, 1904. 

 f Ibid., 1904, vol. x, p. 89. 



