BACTERIAL PRECIPITIN REACTIONS. Ill 



mixtures when he combined precipitating typhoid serum with the serum of typhoid 

 patients. In many cases he obtained these results before the appearance of the Gruber- 

 Widal reaction. 



The method which he has recently employed is known as the "ring test." 



Small test-tubes 8 cm. in height and 0.5 cm. wide, are placed in rows of 

 Fornet's twenty each into a small black test-tube rack so arranged by the help of 

 Ring Test, side stands that the tubes are inclined at an angle of about 45. Across 

 the back of the rack is attached a strip of dark cloth as a background to 

 facilitate the detection of any precipitate. The immune (or convalescent) serum is 

 placed into different tubes in concentrated and diluted form i : 5 and i : 10 with normal 

 saline, and then the serum for examination in concentrated and similar dilutions is care- 

 fully floated on top of the immune serum. The mixtures are allowed to stand undis- 

 turbed at room temperature for two hours, and if the reaction is positive a whitish ring at 

 the point of contact of the two sera, makes its appearance. A control test-tube of 

 normal serum plus immune, and another of normal plus the unknown serum in the same 

 dilutions as those employed in the test, must remain negative. 



Besides in typhoid, the ring test is also evident in scarlet fever, measles and syphilis. 



In syphilis precipitation, the serum from patients with mani- 

 Syphilis fest luetic symptoms is employed as precipitinogen, and the 

 Precipitation, serum from individuals with general paresis acts as precipitat- 

 ing agent. The ring test must be carried out strictly in accord- 

 ance with the rules given by Fornet, but even so, its diagnostic value for 

 syphilis is still doubtful. Plaut claims that normal serum gives the reaction 

 just as often as luetic serum; this is strongly denied by Fornet. 



Theoretically, it is questionable whether these precipitates and rings are 

 similar in origin to bacterial precipitates, or whether physicial-chemical 

 causes are at the bottom of the former phenomenon. In accordance with 

 the latter view several other reactions have been recently recommended 

 for the serum diagnosis of syphilis. 



a. Forges and Meier noticed that luetic sera are capable of producing 

 Forges' flocculent precipitates from lecithin solutions. Forges soon found the 

 Reaction. same occurrence with solutions of bile salts. 



Many additions and modifications have been instituted in the case of 

 Forges' reaction since it was first recommended. According to the most recent publica- 

 tion, the reaction is carried out as follows: 

 The requirements are: 



1. One per cent, solution of sodium glycocholate (Merck) in distilled water. 



2. The patient's serum which must be absolutely clear, and heated for one-half an 

 hour at 56 C. 



Two-tenths of each of the above are placed into a narrow test-tube 6 to 7 mm. in diam- 

 eter, and allowed to rest for sixteen to twenty hours at room temperature. A positive 

 reaction consists of the appearance of distinct coarse flocculi which as a rule, collect near 

 the surface. Mere turbidity or faint precipitates are considered as negative. 



The original Forges method of employment of lecithin was not at all specific, the reac- 

 tion being present in tuberculosis, carcinoma, and other infectious diseases. As for the 

 new modifications, nothing has been brought forward in their support or non-support. 



