406 STATE BOARD OF AGRICULTURE. 



We believe that the title of this paper will permit us to include a 

 few experiments which aimed to determine the effect of the Dorset- 

 Niles serum on hog cholera virus in vitro. We have absolutely no defi- 

 nite knowledge as to the action in vivo of the Dorset-Niles serum. 

 Whether it is antimicrobial, antitoxic, or a promoter of phagocytosis 

 by stimulating the production of opsonins we do not know. It is not 

 easy to determine any of these points. If the serum is antimicrobial, 

 it appears to us that its action on the living cause of hog cholera should 

 take place in a mixture of the two in vitro. If its action is antitoxic, 

 it should at least neutralize any antitoxin produced in vitro. The 

 determination of phagocytosis of an ultravisible organism will require 

 a technic specially devised for the purpose, and probably dissimilar to 

 any with which we are now familiar. 



We have worked upon the hypothesis that if a given amount of serum 

 is required to protect a pig against a given amount of \irus when they 

 arc injected into the pig simultaneously then a less amount of serum 

 will be required to protect against the same amount of virus if the two 

 are mixed in vitro and allowed to remain several hours before injecting 

 into the system of the pig. If a less amount is required then there is 

 evidence of antimicrobial or antitoxic action, probably the former, but 

 if an equal amount of serum is required, then there is no evidence of 

 such action. 



Table X shows that 10 c.c. of Mixed Serum 65 protects against 1 c.c. 

 of virus Expt. 442, but that 5 c.c. does not, either when used in the 

 simultaneous method or after mixing with virus and incubating three 

 hours. As a matter of fact, death occurs eighteen days sooner when the 

 mixture is used than when the serum and virus are used separately. 



Table XI is not very instructive in this connection, since the dispar- 

 ity is great between the amount of serum that is necessary to protect 

 in the simultaneous method and the maximum amount that was used 

 in the in vitro tests. It is seen that 15 c.c. is necessary to protect by the 

 ordinarv method, while we used onlv 5 c.c. in the mixture after incubat- 

 ing two and one-half hours. We have not proved that there is no in vitro 

 action, since our work is too limited in character, but our results indi- 

 cate that it is doubtful whether this line of experimentation will be 

 fruitful of results. 



SUMMARY, 



1. Three pigs were hyperimmunized by injections of (a) B. cholerae 

 suis mixed with pig blood free of the filterable virus, (b) pure cultures 

 of B. cholerae suis, and (c) the filtered virus free of B. cholerae suis 

 respectively. 



2. The serum from the pig hyperimmunized with B. cholerae suis 

 mixed with blood protected a 20 lb. pig in 20 c.c. dose and a 25 lb. pig 

 in 25 c.c. dose. This serum also agglutinated B. cholerae suis at a 

 dilution of 1-12,500. 



3. The serum from the pig hyperimmunized with pure cultures of 

 B. cholerae suis furnished no i)rotection to a 15 lb. ]iig in doses of 20 

 c.c. This senim agglutinated B. cholerae suis when diluted 1-500.000. 



4. The 7)ig hyperimniunizod with the filtered virus free of B. cholerae 

 suis furnished a serum capable of [irotecting a 17 lb. ])ig in 10 c.c. dose 



