Contagious Abortion. 147 



forming bacteria. An attack of cow pox protects the 

 individual against small pox. In fact the beginning of 

 modern vaccination against small pox was due to an ob- 

 servation made by Jenner that people that became in- 

 fected with cow pox did not acquire small pox. Vaccine, 

 which is used as a preventive against small pox, is made 

 by inoculating calves with the virus of cow pox. To 

 make the vaccine the scabs, that form, are removed and 

 ground with glycerine. All the processes are carried out 

 with the greatest care in order to avoid the contamina- 

 tion of the vaccine with organisms that might be injur- 

 ious to the persons vaccinated. 



CONTAGIOUS ABORTION. 



The causes of abortion in cattle may be divided into 

 three classes: (1) abortion caused by mechanical injury 

 or as the result of some other disease, (2) abortion due to 

 the presence of large amounts of smut in the feed, (3) 

 abortion due to the infection of the animal with a spe- 

 cific organism. The first two classes are of interest to us 

 only as they are to be differentiated from the true con- 

 tagious abortion. The cases of abortion belonging in the 

 first class are sporadic and are caused by some injury, 

 such as slipping, falling, being hooked, jammed or 

 kicked. The cases occur singly and no connection be- 

 tween the cases can be traced. 



Ergot or smut of corn and other plants when ingested 

 has such an effect on the uterus as to cause the expulsion 

 of the fetus. If the cause is of this nature a large num- 

 ber of cases of abortion are likely to occur within a short 

 time since all the cattle are under the same conditions. 

 With a change of feed the trouble disappears. Some 



