BUREAU OF ANIMAL INDUSTRY. 121 



Further work is in progress, seeking a solution of the cause of this 

 condition. 



Polyarthritis of hogs and sheep has continued to be the subject of 

 investigation. 



The work of the branch pathological laboratory at South Omaha 

 is represented by 248 specimens sent in from various packing houses 

 within the tributary area. There were received from a locality in 

 Kansas specimens of calves' feces which upon microscopic examina- 

 tion showed that the animals were suffering with coccidial enteritis, 

 a disease which has been very rarely reported in this country. Some 

 other diagnoses of special scientific interest were made. 



BIOCHEMIC DIVISION. 



M. Dorset, Chief. 



RESEARCH WORK ON HOG CHOLERA. 



Further studies of various phases of hog cholera, relating espe- 

 cially to the production of serum, have been made. 



A number of careful tests have demonstrated that hog-cholera 

 serum can not be improved by certain methods that have given good 

 results in the production of rinderpest serum in the work of an in- 

 vestigator (Holmes) in the service of the Government of India. 

 That worker had been able to produce a more potent serum for rin- 

 derpest when the immune serum-producing animal was hyperim- 

 munized within a short time following simultaneous inoculation, and 

 he had also found that a more potent serum could be obtained when 

 the virus used for hyperimmunization was previously diluted with a 

 weak solution of potassium citrate. Owing to the similarity of 

 methods of producing rinderpest and hog-cholera serums, it was 

 thought desirable for the bureau to study the processes with respect to 

 hog cholera. Nonimmune hogs were hyperimmunized at various 

 times following simultaneous inoculation. The results showed that 

 little or no protection could be expected from serum derived from 

 hogs hyperimmunized within 10 days after simultaneous inocula- 

 tion. The serum from hogs hyperimmunized between the tenth and 

 forty-second days possessed more potency than that derived from the 

 hogs hyperimmunized within 10 days, yet was not so satisfactory as 

 that derived from animals held a longer time before hyperimmuniza- 

 tion. Hogs hyperimmunized respectively 49 and 56 days after simul- 

 taneous inoculation produced good serums. Although these experi- 

 ments have been negative in so far as the production of a more potent 

 serum is concerned, they have been of much value in demonstrating, 

 for the benefit of serum producers, that it is unwise to use hogs for 

 serum production unless they have been inoculated simultaneously 

 at least 60 days prior to hyperimmunization. With regard to the use 

 of a diluted virus, it has been determined that this possesses no ad- 

 vantages over the undiluted virus. In fact, so far as this work has 

 gone, the indications are that serum obtained from hogs hyper- 

 immunized with citrated virus is not so potent as that obtained by 

 the use of ordinary defibrinated blood. 



Some experiments were carried out to test the persistence of the 

 virus of hog cholera in the bodies of pigs following simultaneous 

 inoculation. Eighteen pigs were given the simultaneous inoculation. 



