Protective vaccinations 461 



on the other hand, the clavelisation of a healthy flock, beyond the 

 fact that it may cause considerable losses, is attended by the special 

 danger that it creates centres from which the contagion may invade 

 all the flocks of the district 



But there are countries in which protective and general claveli- 

 sation does not present these inconveniences the countries where 

 the disease is endemic and where the sheep are very resistant to the 

 action of its virus. This is the case in Algeria ; sheep-pox exists 

 there permanently without doing much damage; but the Algerian 

 sheep, which take sheep-pox without suffering any apparent illness, 

 communicate to French sheep amongst which they are introduced 

 a very malignant sheep-pox which sometimes kills as many as 50 per 

 cent, of the flock. This explains and justifies the measures recently 

 taken by the Minister of Agriculture, forbidding the importation of 

 Algerian sheep into France unless they have been vaccinated at least 

 a mouth previously. 



In many other countries clavelisation is likewise enacted, being 

 authorised in cases where it may be very useful and interdicted 

 in other cases. In certain countries, e.g. Germany, Holland, and Den- 

 mark, clavelisation can be put into force by the Government, which 

 alone has the right to authorise it under certain circumstances. 1 



III. Antirabic vaccinations. Vaccination against rabies has this 

 point in common with those against small-pox and sheep-pox, that 

 it is effected with a virus whose micro-organism is as yet unknown. 

 On the other hand, it is distinguished by its efficacy during the 

 incubation period. When persons are vaccinated during the incu- 

 bation period of small-pox, or sheep during the same period of 

 sheep-pox, the vaccinations by vaccine and claveau are incapable of 

 arresting the disease and the infections continue to follow their 

 normal course. When, on the other hand, we vaccinate men or 

 animals that have been bitten by mad animals or inoculated with the 

 rabic virus by other means, the antirabic vaccination, with rare 

 exceptions, prevents the development of rabies. This vaccination, 

 taking advantage of the length of the incubation period of rabies, 

 constitutes, therefore, a special type, intermediate between pro- [484] 

 tective vaccination, properly so called, and a therapeutic method 

 of treatment 



1 Nocard et Leclainche, "Les maladies microbiennes des animaux," 2 Edition, 

 Paris, 1898, pp. 464, 469. 



