112 PRECIPITINS. 



This reaction belongs to the same general class of precipitation 



Klausner's tests for lues, but is very much simpler than any of the others. 



Reaction. Two-tenths c.c. of absolutely clear, fresh (at the most, two 



hours old), active serum is mixed with 0.6 c.c. of distilled water, 



in a small test-tube 7 X 0.5 cm. Sera containing hemoglobin or lipoids 



are not suitable for this reaction. The mixtures are allowed to stand at 



room temperature. In several hours, at the latest fifteen, a thick flocculent 



precipitate 2 to 4 mm. high appears at the bottom of the tube. Kreibich's 



analysis showed it to consist of fibrin globulin. 



Apparently this substance is increased in luetic serum and precipitated by the dis- 

 tilled water in which it is insoluble. Klausner's reaction is by no means specific for 

 syphilis as it is in evidence in starvation, typhoid, measles, scarlet, pneumonia, and other 

 diseases, as well as during health. Nevertheless it must be said that it is found more 

 frequently, earlier and much stronger in lues than in any other condition. 



Klausner states that in fresh cases of lues the best reaction is seen in about seven to 

 nine hours, while in older cases a week reaction appears in twelve hours. Mercury 

 influences the test in that the interval until the precipitate becomes marked, is prolonged 

 and later on the precipitate becomes fainter. 



In spite of its simplicity, Klausner's reaction has not been generally adopted for 

 clinical work, inasmuch as the far greater accuracy of the Wassermann reaction has made 

 the latter invaluable. 



Proteid Precipitins. 



While bacterial precipitation is interesting from a biological standpoint 

 but bears no practical significance, proteid precipitation represents one of 

 the most important practical aids in forensic medicine. By this means the 

 differentiation of various proteids can be easily and definitely determined, a 

 problem which was left unsolved by chemistry. 



The phenomenon of protein precipitation is absolutely analogous to 

 that of bacterial precipitation. If a clear proteid solution (a) is mixed with 

 the clear serum (a') of an animal immunized against the above proteid (a) , 

 turbidity and precipitation will occur; while if a mixture of the serum (a') is 

 made with a non-homologous proteid say (b) , or a mixture of the proteid (a) 

 with the serum (b f ) of an animal immunized against b, no precipitation 

 takes place. Graphically expressed it looks thus: 



a + a! = precipitation. 

 b + a' =no precipitation. 

 a + b f =no precipitation. 

 b+b' = precipitation. 



In other words, a precipitating immune serum reacts only with its homol- 

 ogous proteid. The precipitin reaction is specific. 



