BY H G. CHAPMAN 529 



Precipitin aiitisera have also been prepared for ricin,* crotin, 

 and ergot.f These have all shown a high degree of specificity. 



Scope of Inquiry. 



The study of the precipitins, as these bodies came to be called, 

 progressed rapidly in the next few years, since they seemed to 

 be concerned with those specific properties of the components of 

 the tissues of different genera and species which had evaded the 

 chemical tests formerly employed. Some investigators turned 

 their attention to the details of the use of the test for the recog- 

 nition of the blood and proteins of different forms in cases of 

 lesral interest. Others endeavoured to see whether the relations 

 revealed in the zoological kingdom by the biological method were 

 similar to those determined on morphological homologies. Others, 

 again, examined the conditions of formation of these substances 

 in the living bod}' in the hofie that they might lead to further 

 insight into those complex interactions by which the animal 

 organism defends itself against noxious microbic and chemical 

 agents. In this way certain definite paths of research became 

 established. With some of these lines of research the experi- 

 ments recorded in this paper are concerned. In the first place, 

 a furtlier attempt has been made to elucidate the interaction 

 between antiserum and homologous protein with the object of 

 eliciting the quantitative relationships of the i^eaction. In the 

 second place, the knowledge of the numerical relations of anti- 

 serum and protein has been utilised to arrange methods for the 

 differentiation of the proteins of closely allied species, and to 

 render more accurate the diagnosis of the source of individual 

 proteins. In the third place, an attempt has been made to 

 determine by the biological method the relationship of proteins 

 of vegetable origin. The greatly improved knowledge of the 

 technique for the use of precipitins will now enable differences 

 to be recognised in these proteins. And, lastly, the application 

 of the results obtained by gravimetric means to the deviation of 

 complement is pointed out. 



* Jacoby, Hfm. Beitr. i., S. 51, 1901. 

 + Ottoleughi, Biochem. Cent. 1902, No. 1435. 



