IMMUNITY, NATURAL AND ACQUIRED. 



By WILTON W. R. LOYE, MB. 



(Read before the Royal Society of Queensland, 16th Auyust, 1902). 



Immunity is the converse of predisposition. It maybe classified 

 under two great subdivisions, viz., Congenital (natural) and 

 Acquired. 



Congenital (natural) immunity may be an individual 

 peculiarity or it may be common to the species (racial), and 

 in like manner acquired immunity may be temporary or 

 permanent ; in the latter case even it may be transmissible 

 from parent to offspring, hence the term natural is more correct 

 than congenital. Let us take first : — 



Acquired Immunity. — This means that an animal sus- 

 ceptible to an infectious disease may become protected against 

 subsequent infection. This may happen in several ways. 



(A) By Recovery from an attack. 



(B) By inoculation (a) with attenuated virus, i.e., living 

 organisms of low virulence, as in vaccination against sraall-pox ; 

 [h) with small and repeated doses of living and fully virulent 

 organisms, as in the preparation of horses for anti-diphtheritic 

 serum ; (r) with toxins or bacterial products, as in anti-plague 

 prophylactic, i.e., chemical vaccination ; (d) with serum derived 

 from protected animals, e.y., anti-diphthedtic, anti-tetanic, anti- 

 rabic ; ic) by feeding animals with the living organisms or their 

 products — this is meif>ly a sub- phase of the preceding inocu- 

 lation methods of conferring immunity. 



Let us consider each of these methods of establishing an 

 acquired immunity in more detail. 



(A) The natural predisposition to an infective disease may 

 be removed by recovery from an attack. To use Kanthack's 

 words, " this is Nature's way." Certain infective diseases confer 



