My discussion of man in The World will be a little fuller than I had intended, for I have undertaken to explain all the main functions in man. I have already written of the vital functions, such as digestion of food, the heartbeat, the distribution of nourishment, etc., and the five senses. I am now dissecting the heads of various animals, so that I can explain what imagination, memory, etc. consist in. (AT I 263, CSMK 40)