BY H. G. CHAPMAX. 549 



Observations on the Precipitins for Vegetable Proteins. 



Tlie study of the biological relationships of plants by means of 

 precipitins is much more difficult than those of animals. This is 

 -due to the difficult}'' of obtaining material in which reactions, 

 other than those between the interacting precipitin and protein, 

 do not occnr. In the first place, the solution of proteins for 

 intraperitoneal injection of the rabbits must be prepared free 

 from toxic substances. Such solutions must also be sterile. The 

 careful researches* of Dr. J. M. Petrie, in this laboratory, on the 

 seeds of the Acacias, have led to the choice of the proteins of 

 these seeds for preparing the antisera. As further work on the 

 decomposition-products of these proteins is likely to be carried 

 out, and as these proteins may differ widely in chemical pro- 

 perties from the proteins of blood-sera, it may be possible to 

 determine by chemical means whether the precipitates formed in 

 the precipitin reactions are composed of substances akin to the 

 proteins of the Acacias. Recent investigations! of the acidic 

 properties of the proteins and their union with bases, also offer 

 means for the preparation of purer solutions of proteins than 

 have hitherto been obtained. As extracts of the seeds of the 

 Acacias made with 10^ salt solution contain little toxic matter, 

 these extracts have been employed for injection after filtration 

 and dilution. They have been sterilised by heating to 55°C., 

 from 3 to 6 hours. Antisera prepared with heated proteins have 

 been studied by Schmidt. J They may be used for the same 

 purposes as antisera prepared with unheated protein. Similar but; 

 less extensive experiments with antisera made with heated protein 

 have been carried out in this laboratory with the same results. 



The antisera prepared by the injection of these heated proteins 

 have been allowed to interact with solutions of the seeds of 

 different species of plants. The solutions were made by extract- 



* Proc. Linn. Soc. New South Wales, 1908, xxxiii., p. 835. 

 t Brailsford Robertson, " The Proteins," University of CaUfornia Publica- 

 tions, 1909. 



JBiochem Zeitschr. xiv., S.29i, 1908. 



