BLOOD AND THE IDENTIFICATION, ETC. 625 



One general precaution must be mentioned regarding 

 the serum-diagnosis of any disease. Although absurdly 

 obvious, neglect of it has already led into en or; namely, 

 that it is no good applying the test if injections of "anti- 

 toxic " serum have been made and agglutinins thus artificially 

 introduced. 



Not only may the agglutinin reaction be applied to the 

 diagnosis of disease already present, but is also likely to be 

 of use in the discovery of specific micro-organisms as yet 

 unknown, e.o-., small-pox, typhus, measles, etc. For this 

 purpose bacteria must be isolated from the various tissues 

 and their reaction with the serum of patients convalescent 

 from the disease in question ascertained. Naturally, any 

 positive result must be controlled with other sera, and by 

 suitable dilution of the specific serum. 



There is one source of fallacy against which it is neces- 

 sary to guard. Some infectious diseases, c.£:, scarlet fever, 

 and small-pox in its later stages, are nearly certainly cases 

 of mixed infection, more particularly with the organisms of 

 sepsis. Under such conditions more than micro-organism 

 might give a reaction with the serum, and other criteria 

 would have to decide which is the specific one. Partly for 

 this reason I do not consider the coccus above mentioned 

 to be the specific organism of scarlet fever. 



Without Durham and Gruber's exact and complete in- 

 vestigation and extension of the older isolated observations, 

 a valuable addition to both practical bacteriology and to 

 practical medicine would have been, if nothing else, for 

 some time delayed. The application of the serum test to 

 disease in man is but the natural outcome of their work. 

 Being now part of routine diagnosis it is past the stage 

 when the name of any individual should be attached to it, 

 but in the history of this new departure in diagnosis their 

 names have the first claim to be mentioned. 



