po Journal of Agriculture. Victoria. [lo Feb., 1912. 



Preventive Inoculation. — Immunity against blackleg can be pro- 

 duced artificially by subjecting the systemi of an animal to tlie action ol 

 the weakened toxins of the bacillus. This may be done by different 

 methods, but that which has been most successful is the use of a weakened 

 virus or " vaccine " prepared from the diseased flesh according to the 

 method of Arloing. '' P'orty grammes of the diseases muscle are dried 

 rapidly at 32 degrees C. (90 degrees F.) and triturated in 80 grammes of 

 water. This is divided in 12 equal parts and put on plates in two 

 thermostats, six at 100 degrees C. (212 degrees F.) and six at 85 degrees 

 C. (185 degrees F.) where they are kept for six hours, when it forms 

 a dry, brownish powder. One-tenth of a gramme (li gr.) of this powder 

 is dissolved in five grammes of distilled or boiled water and will furnish 

 ten doses. The animal to be protected is first injected in the tip of tl"»e 

 tail or elsewhere with the virus prepared at 100 degrees C, and ten days 

 later with that prepared at 85 degrees C." (Law.) A peculiar fact about 

 the weakened virus so prepared is that its full virulence is regained by 

 the addition to it of a small quantity of lactic acid. 



The Pasteur Institute prepares the vaccine, and issues it in the form 

 of short threads that have been soaked in a virus of required strength 

 and afterwards dried. The threads are introduced under the skin by a 

 special needle after the manner commonly practised in inoculation for 

 pleuropneumonia. An American firm also distributes virus prepared by 

 the Arloing method but in the form of solid pilules which are injected 

 under the skin by means of a syringe fitted with a canula, needle and 

 spring piston. 



F'or the successful prevention of the disease on infected farms or in 

 infected districts all the young cattle between three months and two years 

 old should be inoculated in the spring and autumn. The two inoculations 

 are necessary because the protection which it conveys only lasts about 

 six months. 



It should be mentioned that this method of immunizing stock against 

 blackleg should be restricted to cattle in infected areas otherwise there 

 is grave risk of introducing the disease into new country. Such risk is 

 much greater if the inoculation is carried out during the hot summer 

 season. 



In New South Wales, blackleg is a notifiable disease, the penalty 

 for failure to report being ^50. and for selling or purchasing stock 

 affected with it the fine is ;^ioo. Under the Noxious Microbes Act 1900 

 ])reventive inoculation by private owners without a licence from the Chief 

 Inspector of Stock constitutes an offence. 



