290 COLLECTED STUDIES IN IMMUNITY. 



a preparation containing a mixture of immune sera derived from 

 animals whose receptor apparatus are as divergent as possible." 



Practical results along these lines have already been achieved 

 by Schreiber, 1 who made a hog-cholera serum from horses and oxen; 

 and recently Romer, 2 by paying attention to just this point, has 

 obtained an effective pneumococcus serum by utilizing several differ- 

 ent species of animals. In view of these attempts to apply the 

 above principles practically, it would be regrettable if the untenable 

 Unitarian view maintained by Besredka were to hinder the further 

 development of these methods. 



1 Schreiber, Berlin thierarztl. Wochenschr. 1902, No. 19. 



8 Romer, v. Graefe's Archiv f . Ophthalmologie, Vol. 54, 1902. 



