266 The Older Doctrines [lect. 



"and of retaining, just as if they were made of lead or of wax 

 " as it were, the shape into which they were last thrown until, 

 " by some further action, they are made to assume a new one." 



The ventricles of the brain however do not form the only 

 reservoir of the animal spirits; another and more important 

 reservoir is the pineal gland. This moreover is the only part 

 of the brain to which is attached the rational soul ; this is " the 

 seat of imagination and of common sensation." Through it the 

 rational soul can directly bring about body movements and 

 through it external objects are able to impress the soul. He 

 developes a mechanical theory explaining how the movements 

 of the spirits from the surface of the pineal gland are correlated 

 to the movements of the spirits at the internal surface of the 

 ventricles, the entrance into the pores of the latter affecting 

 the outflow from the pores of the former, and gives an interest- 

 ing exposition of how in the action of external objects on the 

 delicate threads of the nerves there is a double event, a primary 

 event by which impulses from external objects "impress their 

 figure" on the internal surface of the ventricles, and a secondary 

 event by which a corresponding figure is impressed on the 

 surface of the pineal gland and so on the soul. The first, 

 serving as a relay, is as we should say a purely nervous, the 

 latter a psychical, event. 



"Not those figures which are impressed on the external 

 " organs of the senses or on the inner surface of the ventricles 

 " of the brain, but only those which are traced in the spirits on 

 "the surface of the pineal gland can be considered as ideas, 

 " that is to say as the forms or images of which the rational 

 "soul will take direct cognizance, when, being united to the 

 " machine, it imagines or feels any object." 



And he takes advantage of the mobility of the pineal gland 

 to offer a mechanical explanation of psychical phenomena. 

 " Consider moreover that the gland is composed of very soft 

 " material and that it is not completely joined and united to 

 " the substance of the brain but only attached to the small 

 "arteries (the walls of which are very loose and flexible) and 

 " that it is kept balanced by the force of the blood which the 

 "heat of the heart drives towards it. Hence it needs very 



