Baas, History of Medicine, p. 692.
 Based on Thomas H. Huxley's Presidential Address to the British Association for the Advancement of Science, 1870.
 Essays on Digestion, by James Carson. London, 1834, p. 6.
 John Hunter, On the Digestion of the Stomach after Death, first edition, pp. 183-188.
 Erasmus Darwin, The Botanic Garden, pp. 448-453. London, 1799.
CHAPTER V. ANATOMY AND PHYSIOLOGY IN THE NINETEENTH CENTURY
 Baron de Cuvier's Theory of the Earth. New York, 1818, p. 123.
 On the Organs and Mode of Fecundation of Orchidex and Asclepiadea, by Robert Brown, Esq., in Miscellaneous Botanical Works. London, 1866, Vol. I., pp. 511-514.