PROTECTIVE INOCULATIONS. 337 



This secondary virus was very extensively used by Lenglen, a veter- 

 inarian at Arras, who communicated his results to the Academy of 

 Science at Paris, in April, 1863, and Willems says, in his last pub- 

 lished communication, that this is the method which he prefers. It 

 is also the method most extensively employed in Australia, into which 

 country infectious pleuro-pneumonia was introduced in 1858. It 

 (juickly spread and has caused enormous losses. The killing of all 

 animals, sick or suspected of being infected, was tried for several 

 years; but this proved to be ineffectual for stamping out the disease, 

 and the sacrifice was so great that this measure of prophylaxis was 

 abandoned. 



According to Loir, attention in Australia was called to Willems' 

 method of protective inoculations, in 1861, by a letter from Cape 

 Colony published in the journals of Sydney and in Melbourne. The 

 method was at once applied both in Victoria and in New South Wales, 

 and since that date many thousands of cattle have been inoculated. 

 In order to obtain a sufficient supply of virus the method recom- 

 mended by Pasteur in 1882 has been followed. This is described by 

 Pasteur himself in the following words : 



"With a single lung we may procure sufficient virus to serve for numer- 

 ous series of animals. And without having recourse to other lungs this pro- 

 vision may be maintained in the following manner : It is sufficient before the 

 supply of virus is exhausted to inoculate a young calf in the dewlap or in 

 the shoulder. The animal dies very promptly, and all its tissues near the 

 point of inoculation are infiltrated with serum, which is virulent, and may be 

 collected and preserved in a state of purity." 



Loir prefers to obtain the virus in this way from a calf six to twelve 

 months old, during the second week after inoculation, when the tem- 

 perature of the animal has gone up to 40 to 42 C., as the virus is 

 then said to possess the maximum degree of intensity. This vaccine 

 seems to become attenuated in passing through a series of animals by 

 inoculation, so that when it has been passed through a series of five 

 animals it no longer produces death even when inoculated in the most 

 dangerous localities. Loir testifies to the protective value of inocula- 

 tions with this virus made in the tail of the animal, and gives the fol- 

 lowing example : A few months prior to the publication of his paper 

 (1893), about two thousand cows were inoculated with a virus which 

 had been passed through a series of five calves. At the moment of 

 being driven away they were joined by nineteen other cows not vac- 

 cinated. After being on the road for a distance of two thousand kilo- 

 metres, the animals arrived at their destination. The two thousand 

 vaccinated were in good condition, while eight of the non-vaccinated 



had died of pleuro-pneumouia. 

 22 



