CHAPTER VIII 



HEREDITY AND DISEASE 

 " Naturam expellas furca, tamen usque recurbet." — Horace. 



§ I. Health and Disease. 



§ 2. Misunderstandings in regard to the "Inheritance" of 

 Disease. 



§ 3, Are Acquired Diseases transmissible? 



§ 4. Can a Disease be transmitted ? 



§ 5. Predispositions to Disease. 



§ 6. Particular Cases. 



§ 7. Defects, Multiplicities, Malformations, and other Ab- 

 normalities. 



§ 8. Some Provisional Propositions. 



§ 9. Immunity. 

 §10. Note on Chromosomes in Man. 

 § II. Practical Considerations. 



§ I. Health and Disease 



What is Disease ? — The distinction between health and disease 

 is relative to an ideal — the maximum efficiency and well-being of 

 the organism under given conditions ; and pathology, the science 

 of deranged function or disturbed metabolism — deranged or dis- 

 turbed in comparison with what we call " normal " — is, strictly 

 speaking, part of physiology, the science of all vital activity. 

 What we call " normal " in one animal — e.g. a bird's mode of ex- 

 cretion — is called " diseased" in another ; what is normal at one 



250 



