152 Immunity 



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. 



Certain precautions must be observed, though continued 

 study of the subject and the employment of newer methods 

 have shown these to be less numerous. 



For clinical application for typhoid fever diagnosis, com- 

 mercial firms now prepare small cases containing the neces- 

 sary apparatus and " Kicker's solution" of dead typhoid 

 bacilli, so that by following the directions the diagnosis can 

 be made with ease by one inexpert in laboratory manipu- 

 lations. 



In the laboratory the agglutination test may be applied 

 for the diagnosis of any infectious bacterial disease, pro- 

 vided the infecting organism be at hand, or for the recogni- 

 tion of any micro-organism, provided specific serums are 

 at hand, in the following manner: 



If possible, a culture of the microorganism 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 through- 

 out 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 c.c.), to make the fluid opalescent by reflected light though 

 transparent by transmitted light. The same quantity should be added 

 to each, so that they form a uniform series. The serum is next diluted 

 or otherwise added to the tubes, so that they receive different concen- 

 trations in a series from the blood of a patient running, say, i : 10, i : 20, 

 i : 30, i : 40, i : 50, i : 60, i : 80, i : TOO, i : 150, i : 200, i : 300, or a labora- 

 tory series with artificially prepared serums of high value, running, 

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

 or many times higher dilutions. 



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

 covered, and examined in fifteen, thirty, and sixty minutes by simply 

 looking at the dark surface through the fluid. If agglutination occur, 

 the original opalescence gives place to a slightly curdy appearance, 

 as the uniformly suspended bacteria aggregate in clumps. 



If test-tubes are employed, they are best observed by tilting them 

 and looking through a thin layer of the contained fluid at a dark surface 

 or at the sky. In either case the flocculent collections of agglutinated 

 bacteria can be seen. 



The test can also be made and observed under the microscope by 

 the hanging-drop method, but in working with such small quantities 

 much of the accuracy of the technic is apt to be lost. 



Some knowledge is required in order to form correct deductions from 



