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nutshell, for I have already proved, over and over again, that 

 owing to heredity, natural variability, and the acquired 

 modifications wrought by external circumstances, every 

 individual differs from every other, not only physically, but 

 also mentally and morally, and that in every element of his 

 individuality. It is not, therefore, a fact that diseases 

 even those of an acute or exanthematous form differ, or 

 vary in their intensity beyond certain narrow limits, but that 

 the real difference or variation is in the individuals affected, 

 and the difference or variation extends not only to the 

 ultimate elements of his physiological and psychological life 

 to bone, muscle, artery, vein, lymphatics, nerves, blood, 

 plasma, and organs, but also to the constitutional vigour or 

 feebleness the natural power of endurance or intolerance 

 in a word to the vital stamina and energy, which he can 

 summon to resist and overcome morbid processes when they 

 assail him. Disease, is, indeed, the lot of humanity ; but 

 every human unit differs essentially in his inherent and 

 acquired power of resisting and controlling it. Who that 

 has ever attended a family suffering from typhoid, scarlet 

 fever, diphtheria, small-pox, measles, or whooping cough, 

 has not witnessed the protean differences manifested in the 

 several individuals composing it, as to symptoms, intensity, 

 complications, sequelae, and convalescence? There is the 

 disease of a known character and quality, but how different 

 are its effects in the several members of the same family ! 

 Can anyone say that the disease is different in each, or that 

 the intensity of the symptoms in some of them is dependent 

 upon a corresponding intensity of the virus ? Assuredly 

 not ; the real, rational, and only explanation of its different 

 manifestations must be sought and will be found in the 

 inherited and acquired constitutional differences in the 



