796 



THE MECHANISM OF AGGLUTINATION 



substances. The effect of egg albumin on suspensions of mastic described by Michaelis 

 and Rona' is perhaps similar. 



Shibley^ found that in the presence of phosphate ions the critical potential of sen- 

 sitized B. paratyphosus bacteria was raised to 35 mv. instead of the usual 14. Phos- 



J25 



CD 



E 



■- 100 



75 



o 



0.00016 0.0008 0.004 0.02 



Concen+ra+i'on of serum 



1.0 2.0 



Conccn+raHon n NaCI 



8.0 



Fig. 8. — Upper curve: Effect of immune serum on cohesive force in i.o M NaCl. Lower curve: 

 Effect of salt concentration on cohesive force of sensitized and unsensitized smears. 



phate ions, then, according to the present hypothesis must affect the cohesive force as 

 well as the potential. 



A similar effect had been noted by the writer in the case of HCl (Fig. 7). Northrop 

 and Freund^ found that red cells which had been treated either with specific agglutinin, 

 ricin, colloidal stannic hydroxide, or paraffin oil agglutinated at a critical potential of 

 about 12 mv. while the untreated cells remained in suspension until the charge had 



' Michaelis, L., and Rona, P.: Biocheni. Zischr., 2, 219. 1906. 



* Shibley, G.: /. Expcr. Med., 40, 453. 1924. 



3 Northrop, J. H., and Freund, J.: J. General Physiol., 6, 603. 1924. 



