TYPHOID AGGLUTINATION TEST IO9 



dilutions (1-20, 1-40) is not considered characteristic for the 

 t)^hoid organism, since other bacteria may also produce agglutina- 

 tion with the typhoid serum. It is, however, not likely that 

 sera will agglutinate other than the specific one in dilutions as 

 high as 1-80. Higher dilutions should be tried on the principle 

 that the positiveness of the test is in proportion to the serum 

 dilution which will produce clumping. It should also be borne 

 in mind that the agglutination phenomena are more marked at 

 the body temperature (37° C.) and that in the case of the typhoid 

 serum, the paratyphoid group will also give positive results. 

 In reporting on the agglutinating phenomena always give the 

 dilution and the time factors. The novice must frequently be 

 reminded that all manner of solutions of salts, acids, etc., will 

 produce agglutination with most bacteria. We would not 

 recommend the use of the blood-counting pipette (which accom- 

 panies the hemacytometer) for making the dilutions and mixtures 

 of the serum and the bacterial cultures, as is advised by some 

 investigators, largely because of the danger of possible infection 

 in sucking up the quantities of bacteria, and also because this 

 method adds nothing to the value of the results. 



For the so-called macroscopical method or precipitation method, 

 as it is also called, small test-tubes are used in which the suitable 

 dilutions of the serum (with normal salt solution) and the bacterial 

 cultures are mixed. A positive reaction is indicated by flocculency 

 and the deposition of a slight precipitate. Dead (formalized) 

 typhoid cultures may be used. The method in general use in 

 Germany is preferred, a description of which may be found in 

 most text-books on bacteriology. Some of the American pharma- 

 ceutical houses (Parke, Davis & Co.) market a full equipment 

 for making the macroscopic agglutination test with the typhoid 

 germ. It contains full directions for using and according to re- 

 ports is as reliable as this test can be made for practical purposes. 

 It need hardly be stated that in all cases it is desirable to make a 

 control test with normal salt solution. 



