IMMrXITV. J'ACCINES AND SERA 6oi 



(5) Ehrlich's Side-chain Theory. 



Antitoxins and antimicrobic substances are assumed to be normally 

 present in the blood, which when stimulated by the introduction of toxin 

 become increased. A central or mother cell is imagined which throws 

 off two varieties of small cells. These are receptor cells capable of com- 

 bining with food-stuffs for the nourishment of the mother cell. One 

 variety links up with simple food substances, the other breaks down 

 compound bodies preparatory for assimilation. Toxins also have two 

 varieties known as haptophores and toxophores. One becomes fixed 

 to one variety of the receptor cells and the other remaining free, and 

 if in sufBcient numbers, produces toxic changes. 



If the dose of toxin injected is small the mother cells throws off the 

 receptor cell \\ith the toxin attached, such passing free, and now being 

 without harmful effect because it is '' locked up " by the attached 

 receptor. The mother cell produces more receptors so as to exhaust 

 the toxins if these latter are not too excessive. The mother cell then 

 continues to throw off receptor cells into the circulation unfixed, seek- 

 ing toxin cells to fix, but if these latter are exhausted the excess of 

 receptor cells constitutes antitc^xin molecules which are ready to render 

 innocuous or non-toxic an\' new toxic substances of that specific nature 

 which may enter the system. Hence immunity is established, partially 

 or completely, for that specific disease. The toxins may be of the 

 nature of albumoses, and the a.ntiloxins are probably of the nature of 

 globulins. 



The immunity afforded may be feeble and of short duration — 

 weeks, months, or vears. In small-pox seven years or thereabouts. 



After an inoculation there is an increased susceptibility for several 

 days, a condition known as anaphylaxis or a negative phase, conse- 

 quently just after an inoculation there is increased susceptibility 

 towards the disease. Because of this negative stage inoculations 

 should not be given within seven to ten days of the former one. 



Inoculations should be given before the disease is established, 

 during the prodromal period if it is known, or antisera may be given 

 therapeutically during the disease. 



As to plague vaccine, Ilaffkine claims that the case mortality is 

 reduced to less than one-half after inoculation. 



Cholera vaccine gives a marked protection against an attack, but 

 the case mortality amongst the inoculated is not much diminished. 



Antityphoid vaccine reduces the case incidence and case mortality 

 as confirmed in the Great European War. It was only on its trial 

 during the South African War. The protection is not permanent and 

 lasts but from six to twelve months. One could not expect an 

 inoculation to be permanent, really knowing that all the body cells are 

 renewed entirely every seven years or so. 



