20 BULLETIN 106, U. S. DEPARTMENT OF AGRICULTURE. 



Table 3. — Average periods of incubation of abortion. 



Species, source of data, etc. 



Number of 

 animals. 



Average 

 period of 

 pregnancy 

 when inocu- 

 lated. 



Average 



time of 



termination 



of pregnancy. 



Average in- 

 terval be- 

 tween inocu- 

 lation and 

 termination 

 of pregnancy. 



Cows. 

 British Royal Commission : 



7 

 1 



3 



Days. 



71 

 103 



37 



Days. 



189 



254 



172 



Days. 



118 

 151 



Premature births. 



Killed when abortion was apparently threat- 

 ened 









11 



7 



5 



7 



1 

 4 

 1 



65 

 69 



141 



1 



45 

 113 



101 



190 



174 



199 

 199 



128 

 167 

 107 





Killed without symptoms of abortion 



New York State Veterinary College: 



106 



Prof. B. Bang citing Poulsen: 





Ewes. 

 British Royal Commission: 



83 



Lambing (3) or dying at full term from torsion of 

 uterus (1 ) and showing abortion bacilli 



54 



Killed without aborting before lull term and 

 showing abortion bacilli 



6 







Guinea pigs. 



British Royal Commission: 



Aborted and abortion bacilli recovered 



Aborted, but abortion bacilli not recovered... 



1 

 4 



Undet. 

 Undet. 



Undet. 

 Undet. 



19 

 10 





5 

 2 



Undet. 

 34 



Undet. 

 53 



12 



Miches. 



British Royal Commission: 



Aborting, but no abortion bacilli recovered. . . 



20 



3. The data upon the duration of incubation in the cow vary in 

 such a manner as to invite grave doubts as to the reasonableness of 

 the conclusion that the artificially introduced abortion bacillus caused 

 the abortion. Referring again to Table 3, we find that the constancy 

 of the average date of pregnancy at which the cows of various experi- 

 menters aborted is remarkable — 5 by Dr. Moore at the New York 

 State Veterinary College, averaging the one hundred and ninety-ninth 

 day; 11 by the British Royal Commission, averaging the one hundred 

 and ninetieth day; 7 by Poulsen, cited by Bang, the one hundred and 

 ninety-ninth day; and 3 by Bang the two hundred and fourth day. 



In the column recording the period of incubation the same lots 

 show 126, 58, 199, and 114 days, respectively, which gives a very 

 wide and inexplicable variation until a comparative study is made of 

 the date of inoculation. It then appears that the period of pregnancy 

 at which abortion occurred suggests that the duration of incubation 

 is dependent upon the date of inoculation. In other words, inoculate 

 pregnant cows at any date one likes, the average date of pregnancy 

 at which abortion occurs remains the same. We might say that, 

 according to recorded data, the inoculation at any time of a pregnant 



