Contagious Abortion. 417 



portance to recognize the contagion as the essential cause in all 

 cases in which it is present. This can usually be done by a care- 

 ful inquiry into the history of the outbreak. 



When a herd has been continuously healthy up to the date of 

 the introduction of a cow brought from a herd where abortion 

 has been prevailing, and when following her arrival, one after 

 another of the original members of the herd abort, without any 

 apparent cause in the way of change of feed, water, barn, stalls, 

 or general management, the evidence of the introduction of con- 

 tagion by the cow in question is very circumstantial and forcible. 

 If pregnant cows standing next to the new cow, or near to her, 

 abort, the argument for contagion is still further corroborated. 

 If the trouble continues in the herd year after year, attacking 

 fresh animals some months after their purchase, the case becomes 

 still stronger. 



Or if a cow from a healthy herd is sent to a bull, that has been 

 allowed to serve an aborting cow, and if the resulting pregnancy 

 in the first cow is terminated by abortion, and if this is followed 

 by successive abortions in the previously healthy herd, we may 

 reasonably conclude that we are dealing with the infectious form. 

 If no other appreciable cause for the trouble can be found we 

 may reasonably conclude that this was the channel for infection. 



Or a bull is brought from a herd where abortions have taken 

 place, and some time after his arrival, the cows of the previously 

 sound herd begin to abort, the first cases being in those that the 

 new bull has served. The occurrence is manifestly the result of 

 contagion. 



Or a newly purchased cow aborts, and is disposed of in con- 

 sequence, and another cow, placed in the same stall, in due time 

 aborts also, ahd others follow in succession, especially those that 

 stood next or near to the stall in question. Everything points to 

 an introduced infection. 



An indefinite number of other exemplary cases might be 

 adduced, each varying from the last, but all agreeing in this, that 

 the evidence of infection stands out prominently and unmistakably. . 

 The infecting material may have been carried by the tail, tongue, 

 soiled stall, gutter, rubbing post, fence or other object, yet the 

 fact of contagion can be demonstrated with reasonable certainty. 



These conclusions have been repeatedly affirmed by actual 

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