lations were then gradually increased until a sufficient dose 

 was administered to bring about the death of the animal. This 

 result was hastened -toward the end of the experiment by injec- 

 tion of pneuraococci into the left pleural cavity. A sample of 

 blood was taken before each injection and allowed to clot. 

 Two hours later the serum was withdrawn and the opsonic index 

 determined in the manner described above. The normal dogs pro- 

 viding the leucocytes and control serum were always bled at tae 

 same time as the experimental animal. The results of all op- 

 sonic determinations are included in the followinp; tables: 



(10) 



