Change of Corpuscle Resistance. 6i 



A large number of comparative tests are called for, before a defi- 

 nite statement can be made as to whether the increased resistance 

 of the blood corpuscles of immunized animals is due to a change 

 in tonicity of the blood as a whole or simply to a variation in the 

 resistance of the corpuscles. 



34 (290) 



Further observations on the precipitation of inorganic colloids 



by sera. 



By CYRUS W. FIELD. 



\_From the Laboratory of the Department of Health, of New 

 York City.] 



At the meeting of this Society last June, I recorded some facts 

 which seemed to show that in rabbits the precipitating effect of 

 their sera was greater for collodial platinum and collodial silver, 

 after they had received injections of these two substances. Further 

 work since that time on rabbits and on various sera from horses 

 has shown that there are wide variations in the agglutinating or 

 precipitating value for these colloids ; not only in various animals 

 but the value diners in the same animal at different times. 



In a few cases in which I have been able to test the electrical 

 conductivity of the sera, I have found that some of those which 

 gave the highest conductivity gave the highest agglutinating effects, 

 and, therefore, I believe that the variations in the agglutinating or 

 precipitating effect of the sera is due to variations in the concen- 

 tration of electrolytes. These inorganic colloids are, as is well 

 known, extremely susceptible to the influence ef electrolytes and 

 a very slight increase in the concentration of univalent kations 

 and even more especially of the di- and trivalent kations, would 

 cause wide variations in precipitating value. For instance, there 

 might be a greater concentration of one divalent kation and a 

 lessened one of some univalent kation and yet the total concentra- 

 tion of all electrolytes remain nearly the same. 



