The purpose of this supplement is to give a number of these references and to provide a brief, general introduction to some of them. The references are subdivided into groups, each dealing with a branch of the subject. The references in each group are in alphabetical order by name of author (with “anonymous” last), and under each author they are in chronological order by publication date. Some publications, especially a forum or symposium, are listed more than once, according as the topic discussed falls in different groups. In this supplement, the sign three dots ( ...) next to the page numbers for an article indicates that the article is continued on later, nonconsecutive pages. It seemed undesirable to try to make the group of references dealing with a subject absolutely complete, so long as enough were given to provide a good introduction to the subject. It proved impractical to try to make the citation of every single reference technically complete, so long as enough citation was given so that the reference could certainly be found. Furthermore, in a list of more than 250 references, errors are almost certain to occur. If any reader should send me additions or corrections, I shall be more than grateful. THE HUMAN BRAIN No one yet knows specifically how particular ideas are thought about in the human brain. The references listed in this section, however, contain some information about such topics as: The structural differences, development, and evolution of the brains of animals, apes, primitive man, and modern man. The effect on the brain of blood composition, body temperature, supply of oxygen, and other biochemical factors. The structure and physiology of the brain, the nervous system, and nerve impulses. The theory of learning, intelligence, and memory. BARCROFT, JOSEPH, _The Brain and Its Environment_, New Haven: Yale University Press, 1948, 117 pp. BEACH, FRANK A., Payday for Primates, _Natural History_, vol. 56, no. 10, Dec. 1947, pp. 448-451. BEACH, FRANK A., Can Animals Reason? _Natural History_, vol. 57, no. 3, Mar. 1948, pp. 112-116 ... BERRY, R. J. A., _Brain and Mind, or the Nervous System of Man_, New York: The Macmillan Co., 1928, 608 pp. BORING, EDWIN G., _A History of Experimental Psychology_, New York: Century Co., 1929, 699 pp. FRANZ, SHEPHERD I., _The Evolution of an Idea; How the Brain Works_, Los Angeles: University of California, 1929, 35 pp. HERRICK, C. JUDSON, _The Thinking Machine_, Chicago: University of Chicago Press, 1929, 374 pp. HERRICK, C. JUDSON, _Brains of Rats and Men_, Chicago: University of Chicago Press, 1930, 382 pp. LASHLEY, KARL S., _Brain Mechanisms and Intelligence_, Chicago: University of Chicago Press, 1929, 186 pp.