THE PINEAL GLAND 



By ARTHUR DENDY, D.Sc, F.L.S. 



Professor of Zoology in King's College [University of London) 



In a sagittal section of the human brain one sees, projecting 

 upwards and backwards from the thin roof of the thalam- 

 encephalon or 'tween-brain, and lying deep down in the great 

 median fissure which separates the two cerebral hemispheres 

 from one another, a small solid body of about the size of a 

 cherry stone. This body is known to human anatomists as the f 

 " conarium " or " pineal gland " — names which it received from 

 the older writers on account of a supposed resemblance to a 

 pine-cone, while the more general term " epiphysis cerebri " has 

 been applied by students of comparative anatomy to outgrowths 

 of the brain-roof occurring in a corresponding position through- 

 out almost the entire vertebrate series. 



The function of this enigmatical organ had for long been 

 a favourite subject of speculation before the introduction of 

 scientific methods in the nineteenth century made it possible 

 to attack the problem with any hope of success. 



In the first half of the seventeenth century the great French 

 philosopher Descartes bestowed a very large amount of 

 attention upon the structure in question, which, indeed, may 

 be said to have formed the organic centre of his systems of 

 physiology and psychology. As Huxley has said : " The fame 

 of Descartes filled all Europe, and his authority overshadowed 

 it, for a century," and the remarkable views which he held upon 

 this particular subject were no doubt very largely responsible 

 for the special interest which has for so many years attached 

 itself to the pineal gland. It is, therefore, perhaps worth while 

 to devote a little space to the consideration of Descartes' theories. 



In Les Passions de lAme, published in 1650, Descartes 

 discusses the question of the seat of the soul, and concludes 

 that, although the soul is united with the whole body, yet it 

 exercises its functions more particularly in a little gland placed 

 in the middle of the substance of the brain and suspended above 



284 



