Introduction -- The enlargement of parts from increased use, undergrowth and irritation -- Disuse and its effects -- Vestigial parts -- Dichotomy -- Atavism or reversion -- Supernumerary digits, limbs, mammary glands -- The transmission of malformations and acquired defects -- Anatomical peculiarities of the teeth in relation to injury and disease -- Causes of disease -- Inflammation and fever -- Tumours and cancers -- The zoological distribution of disease