31 



we term normal predisposition. Thus the same condition which represents 

 a state of predisposition toward a definite cause of disease can act as a state 

 of immunity to some other cause of disease. Proofs of this are offered by 

 the examples above cited of the hyperacidity of the cell sap which has been 

 shown to give immunity to certain bacterial attacks and predisposition to 

 those of fungi. In the increased sugar content, which is connected with the 

 influence of the acid in increasing the turgidity, we recognize a condition 

 predisposing to injuries arising from frost and, on the other hand, a pre- 

 cautionary means against the disturbing action of drought. 



In the very natural development of the organism, therefore, we con- 

 stantly face conditions of predisposition and immunity. These are present in 

 varying degrees in each individual since each organism has special nutritive 

 relations and utilizes differently the same factors of growth. This explains 

 the phenomenon that dift'erent individuals in the midst of a community of the 

 same species become sick or conversely, in the midst of a centre of disease, 

 remain healthy \ 



9. Inheritance of Diseases and of Predisposition. 



In the last four decades further experiments have been made by many 

 important investigators to explain theoretically the nature of heredity. In 

 this, special consideration was given to the most juvenile condition — the 

 embryonic plasma — as a transmitter of .the capacity for inheritance and the 

 substance which might be indicated as the chief transmitter of inheritance 

 was sought in part in the cell nucleus. 



The above-mentioned hypotheses of biologists were drawn up to explain 

 especially the repetition of the formative processes in the successive genera- 

 tions of the organism. We will call attention only to Darwin's "gemmules," 

 Haeckel's "plastidules," Weismann's "germ plasm" as an '"'heredity plasm," 

 Nageli's "idio-plasm," de Vries' "pangene," etc. 



1 The parasitic theory as generally accepted at present either still needs 

 an explanation of these facts or is restricted to the theory of resistance. The 

 different capacity for resistance to atmospheric extremes and other non-parasitic 

 influences has remained unconsidered. Thus Alfred Fischer* observes "Individual 

 variations indeed occur often enough even in man; a personal immunity of an 

 inexplicable kind seems to exist which in part falls under the conception of predis- 

 position. Even with age natural immunity varies as shown by infantile diseases. 

 The question may be left undiscussed as to whether even these may not be con- 

 sidered as immunizing diseases which are said to prepare the youthful mortal for 

 an existence surrounded by bacteria and to fortify him." 



On the other hand, Alfred Wolff** explains "In all essentials the natural power 

 of resistance to toxins advances in proportion to the organ's capacity to hold the 

 molecules of the poison and to prevent their action on the brain. Thus only quali- 

 tative and no quantitative differences exist between apparently so diametrically 

 opposed phenomena of an innate non-susceptibility and a high grade of susceptibil- 

 ity in individual animal bodies. These differences lie only in the different capacity 

 of the organs in different animal species for the formation of toxin and an eventual 

 neutralization." 



♦Fischer, A., Vorlesungen iiber Bakterien. 2. Ed. p. 347, Jena, Gustav Fischer, 

 1903. 



**Alfred Wolff, Ueber Grundgesetze der Immunitat, Centralbl. f. Bakteriologie, 

 Parasitenkunde usw. Sec. I. Original. Vol. XXXVII. Part 3, p. 701, 1904. 



