SERUM DIAGNOSIS 523 



sometimes j"go on to the formation of a slight papule on the 

 second day ; thereafter the reaction recedes. In the case of 

 syphilitics Noguchi distinguishes three types of positive re- 

 action — (a) papular form, in which a large indurated, reddish 

 papule, 5-10 mm. in diameter, forms and increases for three or 

 four days, the colour becoming dark bluish red ; (b) pustular 

 form, in which the inflammatory change is more severe, the 

 papule changing into a vesicle and then into a pustule; and 

 (c) torpid form, in which, after a latent period of about ten 

 days, reaction appears and goes on to the formation of a small 

 pustule. Noguchi's claims as to the clinical value of the 

 reaction are supported by other observers. The results obtained 

 so far show that a positive result is got when the disease is 

 " latent and often when the Wassermann reaction is negative. It 

 is often absent in secondary syphilis, but may appear after anti- 

 syphilitic treatment has been carried on for some time. Further 

 elucidation of the nature of the reaction is still required. 



Serum Diagnosis — Wassermann Reaction. — The method of 

 applying this test has already been given (p. 127); we have 

 now to consider the results of its application. On com- 

 paring the results obtained it will not be an overestimate to say 

 that a positive result may be obtained in at least 90 per cent, 

 of cases where there is evidence of active general infection. 

 The reaction generally appears first on the fifteenth to thirtieth 

 day after appearance of the sore, and then gradually becomes 

 more marked ; during the period of secondary manifestations it 

 is practically always present ; in the tertiary stage with active 

 manifestations a positive result is only a little less frequent. As 

 the disease becomes inactive or is cured the reaction may disappear, 

 but it is to be noted that disappearance of the reaction after being 

 present does not necessarily imply cure of the disease. It may 

 only have become latent, and on its becoming once more active 

 the reaction may reappear ; in fact, its presence would appear 

 to be definitely related to the activity of the syphilitic lesions. 

 A positive reaction is practically always present in general 

 paralysis and in the large majority of cases of tabes, and may 

 be given by the cerebro-spinal fluid as well as by the blood serum 

 in these diseases. As regards other diseases, a positive reaction 

 has been recorded as occurring in leprosy (p. 308) and 

 sleeping-sickness and also in yaws, and occasionally in malaria ; 

 but (-apart from these diseases it is practically never met with. 

 At present little can be said in explanation of the Wassermann 

 reaction. It seems to depend on the interaction of lipoidal 

 substances in the extract with proteins in the serum, which 



