CONCENTRATION OF ANTIBODIES 



60 to 100 for each dilution, but the number was kept constant for each experiment. 

 The stains used were carbol-thionin and Giemsa's blood stain, but the same stain was 

 used throughout the same series of fluids. 



Inasmuch as there has been so much criticism of the opsonic methods we made 

 the following tests of the accuracy of our observations. Using the same fluids, leuko- 

 cytes, and bacterial suspension, duplicate tests were made. The slides were labeled 

 in such a way that the person making the count had no way of knowing what the slide 

 contained, thus eliminating the personal equation. The result of this test was that 

 while most of the duplicates agreed fairly closely there were cases that varied as much 

 as 25 per cent, but the majority of the counts showed a much closer agreement. 



Bacteriopsonins. We give the results of an experiment which we 

 consider as typical so far as concerns opsonin for Staph. aureus in 

 normal dogs. 



TABLE 12. 

 COMPARATIVE STUDY OF THE OPSONIN FOR STAPH. AUREUS IN THE BODY FLUIDS OF A NORMAL DOG . 



Control = 0.36. 



It will be noted that in this experiment the opsonin had practically 

 disappeared in the dilution of i : 10 in all of the fluids. In the undi- 

 luted fluids the concentration of the opsonin in the serum, neck, and 

 thoracic lymph was nearly the same, but there was a slight excess in 

 favor of the thoracic lymph. The pericardial fluid, cerebrospinal 

 fluid, and the aqueous humor contained opsonin in a very much lower 

 concentration. 



In four of nine normal animals the concentration of the opsonin 

 in the serum was considerably higher than in the thoracic and the 

 neck lymph. In three of nine cases the concentration was practically 

 equal in the serum and the two lymphs. In five of eight experiments 

 the amount of opsonin in the neck lymph was considerably less than 

 in the serum and thoracic lymph. It is thus evident, that, as far as 

 these three fluids are concerned, the concentration is greatest, on the 

 average, in the serum, least in the neck lymph, while the thoracic 

 lymph occupies an intermediate position. 



Opsonin was found in the cerebrospinal fluid of four of seven dogs, 

 but in every case it was in decidedly smaller amounts than in the 

 serum and lymphs of the same animal. In the other three animals 

 there was no opsonin in this fluid. 



