204 STATE BOARD OF AGRICULTURE 



Two noii-pathogeuic strains of Bact. abortus (805 and 1) and two 

 pathogenic strains (300 and 670) as determined by their ability to pro- 

 duce characteristic changes in the organs of guinea pigs were selected 

 for the stud}'. The medium used for cultivation was liver agar pH 6.0. 

 The inoculated media were placed in an improvised Novy anaerobic 

 jar and 10 per cent of the air replaced by OOo gas. The cultures were 

 incubated at 37° C. for 24 hours and transfers made and incubated as 

 before. This procedure was repeated daily for 50 days on the patho- 

 genic strains and for 100 days on the non-pathogenic strains. On each 

 25th day throughout, guinea pigs were inoculated with 0.5 c.c. of a 

 saline suspension of one agar slant (turbidity of suspension by Mc- 

 Farland nephelometer was 3) to determine change in pathogenicity. 

 The pigs were killed at the end of eight weeks and the organs examined 

 for lesions. Agglutination tests were made on the strains with a positive 

 serum and transplants were made and cultured aerobically to determine 

 if they would still grow aerobically. 



The above determinations were made twice, on the 25th and the 

 50th days, for the pathogenic strains, and four times, on the 25th, 50th, 

 75th and 100th days, for the non-pathogenic strains. 



The results are as follows: There was no change in the pathogenicity 

 of the four strains, that is, the non-pathogenic remained non-pathogenic, 

 and the pathogenic strains showed no loss or increase in lesion-produc- 

 ing power. 



The period of cultivation has no influence on the agglutinability of the 

 four strains. 



There was no apparent change in the morphology of the organisms. 



7. Swine Ahortion. 



The studies on swine abortion have been completed for the present. 

 The final results of tUis problem have been submitted for publication in 

 the Michigan Agricultural College Experiment Station Quarterly. The 

 results indicate that swine do not certainly become infected from in- 

 gesting milk containing Bad. ahortus or from associating with infected 

 cows. 



A paper was submitted at the annual meeting of the American Veteri- 

 nary Medical Association by Ward Giltner, R. L. Tweed and I. F. Hud- 

 dleson on ''The role of the udder and its secretion in bovine infectious 

 abortion," and published later in the Journal of the Am. Vet. Med. 

 Assoc, Vol. 15, No. 2, p. 172, 1922. 



There were received during the past year 455 samples of blood (bovine) 

 for diagnosis of infectious abortion of which 136, or 29 per cent, were 

 positive, and 319 were negative to the blood tests. The above number 

 of blood samples does not include those taken from animals in the 

 experimental herd or duplicate tests on herds in which immunization 

 studies are being conducted. 



Our experimental herd at the present time is comprised of 8 cows, 

 10 heifers, 4 calves and 2 bulls. 



[I. Forest Huddleson.] 



