. The Journal of hygiene. ated as indicated in the diagram,follows very closely that shown by the like curve referring to theunvaccinated, in other words, the development of natural immunity dueto age is quite independent of the presence or absence of acquiredimmunity. Lastly, in this connection it is to be noted that the fatalityof the disease increasing with age among peisons who have been vaccinateddoes not indicate a corresponding loss of the protection produced byacquired immunity, because it increases paH passu with that among theunvaccinated. This is shown by diagram III, where it is se
. The Journal of hygiene. ated as indicated in the diagram,follows very closely that shown by the like curve referring to theunvaccinated, in other words, the development of natural immunity dueto age is quite independent of the presence or absence of acquiredimmunity. Lastly, in this connection it is to be noted that the fatalityof the disease increasing with age among peisons who have been vaccinateddoes not indicate a corresponding loss of the protection produced byacquired immunity, because it increases paH passu with that among theunvaccinated. This is shown by diagram III, where it is seen that afterthirty years of age there is no further relative loss in the protectionagainst death displayed by the vaccinated as against the unvaccinated, 534 Immunity Statistics the increase in fatality is due to the lessened capacity for acquiringimmunity, which is a feature shown by the human system in regard tosmall-pox as well as some other diseases, though as before remarked not anecessary consequence of age Diagram III. Diagram showing the manner in which the protection afforded by vaccina-tion decreases. The lowest hne refers to the protection against attack which it isseen nearly vanishes between the ages of 25 and 30. The upper represents the loss ofprotection against death. It is to be noted that while this tends to fall rapidly up tothe age period —30 years, thereafter there is no further loss, so that some permanentchange is made in the tissues by vaccination. The statistics for other towns showessentially the same phenomena. In conclusion, to bring the argument in the preceding pages into linewith the experimental theory of immunity the following points may benoted, Theie are at present two different means known by which anorganism is protected against infective agents, one independent of thecharacter of the body fluids, and the other dependent on the actual presenceor rapid production of certain protective agents in these fluids. Theformer is seen,
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Keywords: ., bookcentury1900, bookdecade1900, booksubjecthygiene, bookyear1901
