780 EXPEHIMKlS'T STATION KECOHD. [Vol.41 



iliased cows, spirilla were associated with the first pregnancy in 6, with the 

 second in 9, with the tliird in 5, and with the fourth in 3 cases. In native 

 cows there were no spirilla associated with the first pregnancy. 1 with the 

 third, 1 with the sixth, and 1 with the eighth. 



A tentative explanation of the fact that thus far spirilla have not been 

 encountered in native heifers of the herd giving birth the first time is that 

 " the young stock is kept segregated from the older and purchased cows until 

 shortly before calving. The occasional discharge of a fetus among the young 

 stock in pasture tends to keep up the disease due to B. abortus. Later on. 

 association with older cows brings about infection with spirilla (F. fetus) and 

 more rarely with other possible agencies of fetal disease. On the other hand, 

 abortions may occur among the pastured stock from time to time and remain 

 unrecognized. Not until both groups of animals are subjected to the same 

 daily scrutiny will it be possible to affirm that abortion associated with spirilla 

 does or does not occur among young stock." 



An interpretation of the agglutination reaction to Bacillus abortus in 75 

 cases of bovine abortion bacteriologically controlled, E. V,'. Smillie, K. B. 

 Little, and L. Florence {Jour. Expt. Med., 30 (1919), No. ^, pp. 341-357) .—This 

 paper gives the results of a study of the agglutination test for B. abortus 

 in 75 of the cases noted in the above article, together with tests for B. abortus 

 in the milk in certain cases. 



Of 19 cases in which spirilla were found, 11 gave negative results in the 

 agglutination test for B. abortus (considering an agglutination titer up to and 

 including 1:40 as negative). In 2 cases a maximum titer of 1:1280 for 

 B. abortus was associated with the presence of this bacillus in the milk. In 

 4 cases the titer indicated an earlier infection with B. abortus, the milk tests 

 of 3 of these cases being negative. One case showed a remarkable rise in 

 agglutination titer following the discharge of a fetus containing spirilla, but 

 not B. abortus. One case gave a titer of 1:640 after an abortion associated 

 with positive spirilla cultures and negative tests in the milk. 



Of 11 cases of abortion characterized by sterile fetuses or by miscellaneous 

 infection of the digestive and respiratory tracts, 8 showed a titer of 1 :20 or 

 lower. The higher titers in the other cases could be explained by earlier 

 B. abortus infection. Of 44 cases of abortion associated with B. abortus in 

 the fetus, the membranes, or the udder, agglutination titers of less than 1 : SO 

 were obtained in 8 cases, of 1 : 80 in 2, of 1 ; 160 in 3, of 1 : 320 in 6, of 1 : 640 

 in 16, and 1 : 1280 In 9 cases. 



The authors conclude as a result of these observations that, although no 

 definite rules can be formulated for the interpretation of the agglutination 

 reaction quantitatively, it is, when so carried out as to give the entire range 

 of serum dilutions to the limits of clumping, a delicate test which reflects a 

 variety of conditions involved in infection with B. abortus, such as its time 

 relation to the act of abortion and the length of time the abortion bacilli live 

 and multiply in the pregnant uterus. In the individual cow, in general, a 

 titer of 1 : 40 or less is thought to indicate that the cow is not infected with 

 B. abortus at the time of blood examination. It does not, however, exclude 

 former infections in the case of older cows, nor exclude absolutely very recent 

 infection. The highest titers, 1:640 and above, are considered to indicate 

 recent infection and, in the absence of recent premature births, infection of 

 the udder. Intermediate titers may indicate a gradual rise or decline of 

 agglutinins preceding or following abortion without infection of the udder, 

 or a relatively high resistance or partial immunity in the cow. 



"In any herd a uniniiiiily iov/ titer (1:40 or less) in all animals may be 

 regarded us indieaLing the entire absence of B. abortus. A high titer in any 



