(1) The review of the published data furnishes additional evidence in support of the view that no technique whatsoever, Dreyer's technique included, based on the quantitative method of the agglutination reaction hitherto used, is capable of affording a differentiation between inoculation and infection agglutinins.(2) These techniques are concerned always exclusively in the demonstration of the labilotropic H agglutinins ofB. typhosusandB. paratyphosusA. and B. and it is the behaviour of these agglutinins that is the responsible factor in producing the phenomena.(3) In various febrile conditions in inoculated individuals these H agglutinins undergo a re-stimulation resulting in a curve of agglutination which is indistinguishable from that due to specific stimulation. The re-stimulation of the labilotropic inoculation agglutinins is of the same nonspecific character (i.e.heterologous) in the course of enteric infections as in the course of other febrile diseases.(4) The observation of this non-specific re-stimulation is independent of the technique used; living bacilli and suspensions preserved with phenol or formalin (Dreyer's technique included) do not in this respect behave differently.(5) The proposed qualitative method for the Widal test depends, in inoculated individuals, exclusively upon the behaviour of the stabilotropic O agglutinins. In their presence it is capable of affording the certain diagnosis of an enteric infection; in their absence the negative result of the test is not conclusive; if T.A.B. vaccine has been used it is only possible to diagnose enteric group without being able to differentiate typhoid from paratyphoid A. or B.; if T. vaccine has been used then A. or B. infection can be differentiated but not T.(1) The conclusions previously arrived at by means of the qualitative method of the Widal test were fully confirmed. By eliminating the labilotropic H agglutinins from any consideration—in the case of previously sensibilised individuals—agglutination due to the specific stimulation in active enteric infection can be distinguished definitely from that due to the nonspecific re-stimulation by various febrile diseases.(2) Normal and immune O agglutinins forB. typhosusandB. paratyphosusA. and B., as well as those forB. proteusX 19, are not liable to non-specific stimulation in the course of various febrile diseases.(3) One more of the supposed differences in nature between the Widal test and the Weil-Felix test is thereby eliminated.(4) The difference in the response to non-specific stimulation shown to exist in stabilotropic and labilotropic agglutination seems more likely to be one of degree than one in nature and needs further investigation.