THE WONDERS OF LIFE 



the phronema is the organ of thought in the same sense 

 in which we consider the eye the organ of vision, or the 

 heart the central organ of circulation. With the destruc- 

 tion of the organ its function disappears. In opposition 

 to this biological and empirically grounded theory, the 

 current metaphysical psychology regards the brain as 

 the seat of the soul, only in a very different sense. It 

 has a strictly dualistic conception of the human soul as 

 a being apart, only dwelling in the brain (like a snail in 

 its shell) for a time. At the death of the brain it is 

 supposed to live on, and indeed for all eternity. The 

 immortal soul, on this theory (which we can trace to 

 Plato), is an immaterial entity, feeling, thinking, and 

 acting independently, and only using the material body 

 as a temporary implement. The well-known "piano- 

 theory" compares the soul to a musician who plays an 

 interesting piece (the individual life) on the instrument 

 of the body, and then deserts it, to live forever on its 

 own account. According to Descartes, who insured the 

 widest acceptance for Plato's dualistic mysticism, the 

 proper habitation of the soul in the brain — in the music- 

 room — is the pineal gland, a posterior section of the 

 middle-brain (the second embryonic cerebral vesicle). 

 The famous pineal gland has lately been recognized by 

 comparative anatomists as the rudiment of a single organ 

 of vision, the pineal eye (which is still found in certain 

 reptiles). Moreover, not one of the innumerable psychol- 

 ogists who seek the seat of the soul in some part of the 

 body, after the fashion of Plato, has yet formulated a 

 plausible theory of the connection of mind and body and 

 the nature of their reciprocal action. On our monistic 

 principles the answer to this question is very simple, 

 and consonant with experience. In view of its extreme 

 importance, it is advisable to devote at least a few lines 

 to the consideration of the phronema in the light of 

 anatomy, physiology, ontogeny, and phylogeny. 



i6 



