450 THE TECHNIC OF COMPLEMENT-FIXATION REACTIONS 



employed that eliminates one possible source of error, due to the 

 natural antisheep amboceptor in human serum. 



Noguchi advocated the use of active serum for this test, with an 

 antigen of acetone-insoluble lipoids. Active serum yields a more 

 delicate reaction, but may give false or proteotropic complement 

 fixation, especially when crude alcoholic extracts are used as antigens. 

 Before I began using cholesterinized alcoholic extracts in making the 

 Wassermann reaction I not infrequently found that the Noguchi test 

 with active serum was more delicate than the Wassermann reaction, 

 but with cholesterinized extracts the results ran closely parallel. It 

 is a good practice to conduct both a Wassermann and a Noguchi test 

 with each serum, as a negative Noguchi test with active serum is a 

 better indication of the absence of syphilis than is a negative Wasser- 

 mann reaction. A positive Wassermann reaction, however, is better 

 evidence of the presence of syphilis than is a positive Noguchi reaction, 

 because of the possibility of false complement fixation occurring in 

 the latter when active serums are used. I may state, however, that 

 when a good antigen of acetone-insoluble lipoids is used, the per- 

 centage of false reactions is relatively small, being less than 2 per 

 cent. The Noguchi test, on the other hand, may be conducted with 

 inactivated serums, when the danger of false reactions is removed, 

 but the delicacy of the test is likewise diminished, so that it more 

 closely approaches the Wassermann reaction. 



Noguchi endeavored to simplify the technic of the syphilis reaction 

 by preparing complement, antigen, and amboceptor dried on filter- 

 paper. These were titrated and so adjusted that a certain measure 

 of paper represented the required amount of each reagent. In this 

 manner it would be possible for a large central laboratory to prepare 

 and standardize these reagents, putting them up ready for use in the 

 simplest possible form, and thus making them available for the 

 practising physician. Complement, however, deteriorates so rapidly 

 that the paper is useless unless it is freshly prepared. The antigen 

 slips likewise deteriorate, but not so rapidly as the complement; the 

 amboceptor, however, is well preserved by this method, and forms 

 a simple method for titrating and handling this important reagent. 



Technic of the Noguchi Modification. (1) Complement is fur- 

 nished by the fresh, clear serum of the guinea-pig, put up in 40 per 

 cent, solution, prepared by diluting 1 part of serum with \Y^ parts of 

 normal salt solution. Dose 0.1 c.c. (5 drops from a capillary pipet). 

 Whenever possible it is always best to use a mixture of the serums 

 from two or more guinea-pigs. 



