EXPERIMENT STATION BULLETINS. 441 



AGGLUTINATION. 



The blood of normal (untreated pigs) may agghitiuate virulent cult- 

 ures of B. clwlerae snis in dilutions as high as 1-250, usually less. The 

 blood of young pigs contains less agglutinin as a rule than that of old 

 pigs. 



The blood of pigs having hog cholera as a result of virus inoculation 

 may agglutinate B. clwlerae snis in dilution as high as 1-800 but usually 

 at a less dilution. Here again age is a factor in that old pigs develop 

 more agglutinin than young ones. (Old pigs are likewise more resist- 

 ant to hog cholera infection.) 



The blood of pigs treated by the serum-simultaneous method may 

 agglutinate B. cholerae suis in dilutions as high as 1-500. 



The agglutination reaction seems to be one of immunity not of in- 

 fection, at least, agglutinins develop in connection with immunity but 

 perhaps not as a factor in the condition of immunity. This deduction 

 is based upon the observation that a large percentage of pigs treated 

 by the serum-simultaneous method show a low agglutinative power in 

 the event of death, while of those that live 50 per cent, show the high- 

 est agglutinative jjower. 



During tbe process of hyperimmunization, the agglutinin content of 

 a pig's serum increases as a rule as the amount injected increases, and 

 may fall during the tail bleedings unless more virus be injected. 



If the agglutinogen in the virus is B. cholerae snis then the quantity 

 of agglutinogen (number of B. clwlerae snis) injected into a large 

 serum hog during the whole process of hyperimmunization would 

 ordinarily (if only freshly drawn virus is used) be less than would 

 be contained in .10 cc. of a 21-hour bouillon culture of B. cholerae suis. 



The injection of a number of B. cholerae suis, in bouillon culture, 

 equal to that found in the total quantity of virus sufficient to hyperim- 

 munize a large pig fails to stimulate the production of agglutinin to 

 such an extent as is the case when the virus is injected. 



Over one-third of the cases of serum hogs studied furnish a serum 

 agglutinating at a dilution of 1-50,000. 



The Dorset-Niles serum retains its agglutinative power for several 

 days, almost unimpaired, when preserved in .5 per cent, carbolic acid, 

 trikresol or formalin. The agglutinative power of a serum may dimin- 

 ish 50 per cent., more or less, after a period of 6 to 8 months. 



The potency of the Dorset-Niles serum, the biological test being 

 the standard, cannot be measured uniformly by its agglutinative power 

 for B. cholerae suis. However, the biological test with pigs is a varia- 

 ble standard. 



Sera of high agglutinative power, i. e., reacting at 1-2,000 or above, 

 were potent in 85.71 per cent, of cases and not potent in 14.28 per 

 cent.; sera of low agglutinative power, i. e., reacting at 1-1,000 or less, 

 were potent in 45.45 i^er cent, of cases and not potent in 54.54 per cent. 



The agglutinability of the ditferent cultures used by us indicates that 

 they belong to the same strain. They were isolated from the spleen 



Note. — The maximum agglutination titer for pigs treated by the i^erum- simultaneous method is 

 less than for pigs treated with virus only. This is because the former were all young pigs while 

 the latt-r were mostly old. Comparing pigs of nearly equal size, those receiving 1 c. c. of virus 

 only showed an average agglutinative power of 1-197, w-hile those receiving 1 c. c. of virus and 

 the Dorset-Niles serum showed an average agglutinative power of 1-262. 



