466 IMMUNOLOGY 



existing tests. Tliis increased sensitivity is secured by addition 

 of both cholesterol and sitosterol to the antigen and a modification 

 in manipulation. 



Rosenthal Test. — Rosenthal (1929) has reported a new sensi- 

 tive flocculation test. This increased sensitivity is accomplished 

 through an increase in the cholesterol content of the reacting 

 mixture. The antigen is essentially a Kahn antigen without the 

 addition of cholesterol. Equal parts of cholesterol solution (2 

 per cent in acetone) and antigen are mixed. Fifty milligrams 

 of methylene blue are added to 10 c.c. of the mixed reagent. This 

 dye stains the particles. A drop of the stained antigen is added 

 to four drops of inactivated serum. Examination is made with 

 a magnification of 80 to 100 diameter. Clumping occurs in syph- 

 ilitic serum. 



Mazzini Microflocculation Test. — In the Mazzini (1939) test the 

 antigen contains acetone insoluble, alcohol soluble lipoids from 

 both dehydrated beef powder and powdered egg yolk, and also 

 cholesterol and buffered saline. The student is referred to 

 Mazzini 's publication for a description of the test. According to 

 Ratcliffe (1940) the Mazzini test is superior to "certain other 

 tests in common use." 



It has been impossible to discuss in the space of one chapter 

 all of the flocculation reactions used in the serological diagnosis 

 of syphilis. Outstanding types of reactions have been cited as 

 examples to establish general principles. Thi.s policy has, per- 

 haps, led to the omission of many valuable and efficient procedures. 



Importance of Using- Both Complement Fixation and Precipita- 

 tion Tests.- — None of the methods described will replace the com- 

 plement fixation methods entirely. There are sera which will 

 give positive flocculation tests and negative complement fixation 

 tests. The reverse is also true. It would seem better practice 

 to use both the flocculation and complement fixation tests as 

 routine procedures. It will greatly increase the accuracy of the 

 results and reduce the number of false reactions to a minimum. 



Hypersensitive Tests of Doubtful Value. — The use of hyper- 

 sensitive tests, either complement fixation or flocculation, is con- 

 demned by Levine (1533). Transitions from primary to early 

 and to later secondary stages are associated with definite changes 



