PRECIPITINS 137 



Uhlenhuth showed that by treating a rabbit with 

 chicken albumin a precipitin is formed which pre- 

 cipitates chicken albumin. Myers, by treating ani- 

 mals with Witte's pepton and globulin, produced a 

 serum that contained specific antipeptons and anti- 

 globulins. Pick and Spiro, by using albumose, 

 produced antialbumoses. Leclainche and Vall6e, 

 Stern, Mertens, and Ziilzer treated animals with 

 human albuminous urine and produced a serum 

 which contained a precipitin specific for this sub- 

 stance. Schiitze, by treating rabbits with a vege- 

 table albumin, as well as with human myoalbumin, 

 produced a precipitin specific for these albumins. 

 This does not exhaust the recital of the work done 

 in this field, and there is a host of other albuminous 

 bodies which, when injected into an animal, are 

 able to excite the production of precipitins. 



Specificity of the Precipitins. It was soon recog- 

 nized that the specificity is not absolute. Above all, 

 this depends upon the strength of the serum, i.e., 

 its degree of activity. This is measured by the 

 dilution in which it will still react. Thus a highly 

 active serum, one, for example, which will still 

 give a distinct reaction when diluted i : 1000 or over, 

 will produce a marked precipitate with the serum 

 used to excite its production ; whereas, in the serum 

 of other animal species it will produce slighter pre- 

 cipitates, or only cloudings. A less highly active 

 serum will likewise cause a marked precipitate in. 



