24 



for pleuro-pneumonia, inasmuch as a completely recovered animal is 

 harmless ; only such animals in which the sequesters have been found 

 in the lungs carry the contagion with them as long as this sequester has 

 access to a bronchus. 



Immune Serum. 



The recovery from an infection is accompanied with the acquisition 

 of certain qualities of the blood, more particularly of its serum ; the most 

 prominent one of which is the preventive effect such a serum exerts on the 

 virus to which it corresponds, when injected previously, simultaneously, 

 or subsequently to the virus or when mixed with the virus, either totally 

 or partially prohibiting the effect of such virus. In addition to this, in 

 certain cases direct influences are noted in vitro on the virus known as 

 precipitation, agglutination and cytolysis (Bacteriolysis). These quahties 

 become specially pronounced in hyperimmune animals, which process is 

 carried out by subcutaneous or intrajugular injections of large amounts 

 of virus. In rinderpest the injection of an appropriate dose of serum 

 some hours previous to virus prevents the latter from developing ; when 

 injected simultaneously, a reaction ensues which, in the majority of cases, 

 ends with recovery. The same can be noticed when the serum is injected 

 not too long after the virus ; the action of the virus is completely 

 destroyed when it is mixed in vitro and then injected. In pleuro- 

 pneumonia, according to Nocard, the inoculation of an immune serum 

 (40 c.c.) protects against a subsequent inoculation of virus (1 c.c). In a 

 mixture of serum and virus in equal quantities injected subcutaneously, 

 the virus does not develop. In quarter-evil, according to Kitt, an 

 immune serum (40 c.c.) injected some days previously to virus protects 

 against this virus. In a mixture of serum and virus injected sub- 

 cutaneously, the virus becomes inert. The serum has agglutinating 

 properties. In anthrax an immune serum protects against a subsequent 

 virus injection. A simultaneous inoculation of serum and virus produces 

 active immunity (Sobernheim). 



The resume concerning immunity in non-tropical diseases may be 

 classified as follows : — 



(1) Immunity may be complete, both regarding quantity of virus 



and length of time it lasts. 



(2) Immunity lasts only for a limited time. 



(3) Immunity varies with the quantity of injected virus. 



(4) Immunity varies with the virulency of the virus used. 



(5) Immunity renders an animal unfit for the propagation of the 



contagion. 



(6) Immunity and the process of hyperimmunisation gives the 



serum preventive qualities. 



