706 



THE AGRICULT 



URAL JOURNAL. 



a lierd would have to be sacrificed in 

 order to furnish iuocnlative material for 

 the remaining 95 animals. This propor- 

 tion is being observed at present in the 

 Cape Colony, and also in Natal, and is 

 found to be about sufficient to adjust the 

 variation of yield as above. As the 

 amount of bile necessary for the effective 

 immunisation of an animal is from 20 to 

 25 centimeters (10 for the first and 10-15 

 for the second it will be seen, on the 

 above computation, that the yield of use- 

 ful bile from each animal averages about 

 400 to 500c.c.m. This is probably near 

 the mark, for although we frequently 

 meet with small and useless galls upon 

 opening a beast, we sometimes find dis- 

 tended and fully developed gall-bladders 

 containing more than doable the above 

 quantity. 



It will thus be seen that the bile method 

 of immunisation can only be applied at a 

 cost of one animal in every twenty to be 

 protected. This must be a serious 

 economic consideration where it is neces- 

 sary, generally, to a lopt such preventive 

 measures throughout the length and 

 breadth of the land. If a permanent 

 degree of imminiity could be purchased 

 at such a price, the sacrifice might be 

 made more readily, but if there exists 

 the possibility of the disease levying 

 upon tne horned stock of the Colony a 

 periodical toll of 5 per cent., the question 

 becomes more serious. 



We cannot rely upon the immunity 

 conferred by bile standing us in good 

 stead for future outbreaks of the disease, 

 and only the improvident and sanguine 

 man will seriously entertain the impro- 

 bability of non-recurrence in the future, 

 or found his hope of escape upon the 

 efficiency of our State machinery for sup- 

 pression. Rinderpest laughs at restric- 

 tion^, and the future holds n > certain 

 warranty against recurrence. 



In considering the practical application 

 of the method, it is noticed that a definite 

 relation seems to exist between the dose 

 or quantity of (he bile injected, and the 

 degree of the immunity conferred. The 

 dose of iOcc.m. has been decided upon 

 as being the least practicable dose which 

 will prove efficacious. Smaller doses of 

 l)ilepe] niit the disease to establish a foot- 

 hold to a greater or less degree, and it 

 has been I'onud by experiment that 



animals receiving 5 c.c.m. or less are 

 unable to resist a fatal attack when 

 injected subsequently with virulent 

 blood. If the degree of immunity bears 

 a definite relation to the amount of the 

 injection — as it thus seems to do — a 

 stronger and mo'-e permanent im nunity 

 will be conferred by a larger dose of bile 

 than lO c.c.m., though the immunity pro- 

 duced by even a large injection of bile 

 would never probably equal the per- 

 manency of an " active " immunity, such 

 as is enjoyed by the animal surviving an 

 actudl attack of disease. Even if this 

 immunity were approached, the wide ap- 

 plication of such a principle would become 

 impossible for economic reasons. 



The double injection of bile, now so 

 generally adopted, has several points in 

 its favour. It is improbable that the same 

 benefic'al effects would follow a single 

 injection of a quantity equal to the sum 

 of the double injection. 



It is indeed reasonable to suppose that 

 the immunity obtainable by five succes- 

 sive injections of five centimettrs of bile 

 at definite intervals, would e-xceed the 

 immunity acquired by a single dose of 25 

 ceniimeters. The most obvious advantage 

 claimed for the double injection, how- 

 ever, seems to be that by the first dose of 

 glycerinated bile, the animal is enabled 

 to withstand a subsequent dose of pure or 

 undiluted bile without incurring any risk 

 of contracting the disease through its in- 

 jection. By this means it is claimed that 

 th3 bile system is rendered absolutely 

 devoid of risk of spreading the disease, 

 and there is no evidence to challenge or 

 refute so important a claim, and it cannot 

 be denied that by the second dose of pure 

 bile, the frail immunity of the first 

 glycerinated injection is confirmed and 

 strengthened. 



One of the most important modifica- 

 tions of this system is the attempt to pro- 

 duce from the passive or temporary im- 

 munity produced by bile, a form of per- 

 mment or active immu.iity by the intro- 

 ductioj) into the animal's system of the 

 actual contagion of the disease. This, as 

 will be seen, is an important point, 

 although ihe objection to its adoption 

 can be understood, particularly where the 

 degree of the immunity conferred by the 

 bile cannot be estimated. 



(To be continued,)} 



