THE PRECIPITINS AND THEIR ANTIBODIES 287 



ulates, so that it loses its solubility in weak acids. In 

 this point it differs from the lacto-serum precipitate and 

 from agglutinated bacteria, which lose their agglutination 

 at high temperatures. It is soluble in concentrated solu- 

 tions of urea or magnesium chloride or in formalin. In 

 this point it resembles agglutinated bacteria. 



A great practical importance is attached to the examina- 

 tion of the properties of serum-precipitins, prepared by 

 the injection of serum from one animal into the veins of 

 another animal. These precipitins are to a high degree 

 specific, and they have therefore been used to determine the 

 origin of blood-flecks for forensic or medico-legal purposes. 

 On this point it may be sufficient here to refer to the 

 investigations of Uhlenhuth, 1 Wassermann and Schutze, 2 

 and Hamburger. 3 



Recently Hamburger 4 has executed some quantitative 

 experiments on the action of these precipitins. He meas- 

 ured the precipitate formed in the reaction between a 

 certain quantity of a blood-serum and its antibody pro- 

 duced by the repeated injections of this serum into the 

 veins of another animal. The reacting fluids were mixed 

 in a funnel-shaped vessel which extended into a capillary 

 tube of uniform calibre and graduated in 100 divisions. 

 By vigorous centrifugation of this vessel for 1.5 to 2 hours 

 he packed the precipitate into the capillary tube, where it 

 reached a constant volume and was measured by the read- 

 ing of the divisions. 



1 Uhlenhuth: Deutsche med. Wochenschrift, No. 30, p. 499 (1901). 



2 Wassermann and Schutze : Berl. klin. Wochenschrift (1901). 

 8 Hamburger: Deutsche med. Wochenschrift, No. 6 (1905). 



* Hamburger: Folia hcematologica, Vol. 2, No. 8 (1905). 



