202 THE PRINCIPLES OF IMMUNOLOGY 



panosomiasis and certain skin diseases. Gordon, Thomson and Mills 

 have recently insisted that malaria will not produce a positive re- 

 action unless complicated by syphilis or as the result of faulty technic. 

 Although a controversial point, we believe that occasional cases of 

 tuberculosis may give a positive Wassermann test. That this is not 

 necessarily due to coincident infection with syphilis is shown by the 

 experience of Petroff, who found a positive Wassermann in a 

 tuberculous cow. 



Interpretation of Results. Craig and others are of the opinion that 

 a strongly positive result, such as would be indicated by -| | | |- in 

 our schedule, is conclusive evidence of syphilis, whether there are 

 symptoms or not. Other degrees of fixation must be interpreted with 

 the aid of clinical history and symptoms. A single negative reaction 

 does not exclude syphilis. In doubtful cases the so-called provocative 

 treatment should be applied. This means that a short course of mer- 

 cury or preferably half the usual dose of salvarsan or neosalvarsan 

 should be given and the Wassermann test made subsequently. It is 

 advisable to test the blood twelve, and twenty-four hours after pro- 

 vocative administration of salvarsan as well as every day for at least 

 ten days. If the reaction is to become positive, it usually does so in 

 from a few hours to five or six days, but may be delayed for ten days 

 or even more. That this is an absolutely specific effect of the drug is 

 contradicted by the report of Wildgren, who found that the injection 

 of milk may produce similar results. Endless discussion might be pre- 

 sented as to the interpretation of the Wassermann test in the clinical 

 diagnosis of syphilis, but we incline to the view that this test, as is 

 true of many laboratory examinations, is to be regarded as important 

 evidence in clinical diagnosis, is of striking specificity when properly 

 performed, but is not absolutely pathognomonic. 



Dependability of the Test. Criticism has been directed against 

 the test because of the fact that results do not always agree with 

 clinical findings and because of differences in results upon the same 

 serum in different laboratories. It must be admitted that the factors 

 of error in the test are greater than in clinical diagnosis of the disease. 

 Discrepancies in reports from different laboratories may, in part, be 

 due to inherent faults in the test, to faults in technic, to faults in selec- 

 tion of materials and to insufficient training of the worker. The older 

 literature contains serious criticisms of the test, as for example the 

 papers of Wolbart and of Uhle and Mackinney. Under the direction 

 of the Medical Research Committee of Great Britain in 1918 the results 

 obtained independently by Dr. C. H. Browning, Dr. J. Mclntosh and 

 Col. L. W. Harrison upon the same specimens are in very close agree- 

 ment. More recently Solomon has analyzed the results of 3000 tests 

 carried out in two different laboratories by skilled workers, Dr. Hinton 

 and Dr. Castleman. There was complete agreement of results in 93.44 

 per cent, of this large series of tests. This study demonstrates that 

 with modern methods and skillful performance of the test results are 

 highly dependable. 



