PRECIPITATION TESTS IN TYPHOID FEVER 123 



bouillon cultures of pneumococci, rhinoscleroma, and ozoena bacilli. The immune 

 serum was obtained from rabbits which had received four to five subcutaneous injec- 

 tions of the respective bacterial suspensions. 



Fornet has recently advocated the precipitation test as an aid in the 

 clinical diagnosis of typhoid fever. Although his attempts have not 

 been attended with practical success, the principles of the reaction de- 

 serve discussion on account of their originality. 



Fornet believed that it should be possible to demonstrate in the blood of typhoid 

 patients the presence of the antigens (precipitinogens) which stimulate the antibodies, 

 long before the latter themselves become evident. He actually was able to obtain 

 turbid 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 in 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 in tubes in concentrated and diluted form 1:5 and 1:10 with normal 



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



carefully floated on top of the immune serum. The mixtures are allowed to stand 



undisturbed 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 fever, the ring test is also evident in scarlet fever, measles and 

 syphilis. 



For the precipitation test in syphilis, the serum from patients 



Syphilis with manifest luetic symptoms is employed as precipitinogen, 



Precipitation, and the serum from individuals with general paresis acts as 



precipitating agent. The ring test must be carried out strictly 

 in accordance 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 physical-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 made to the Forges' 



