30 4 SCIENCE PROGRESS 



disgust and aversion by associative memory. As Gallon in his 

 inquiries into the human faculties truly remarks : " The furniture 

 of a man's mind chiefly consists of his recollections and the 

 bonds that unite them. As all this is the fruit of experience it 

 must differ greatly in different minds according to their indi- 

 vidual experiences." 



A glance at this diagram of a section of the brain of a three 

 months' child shows you that the whole of the white matter now 

 contains myelinated fibres and all the primary projection centres 

 are associated one with another (Plate V, fig. 2). 



The Anatomical Substratum of Mind. — The proportional 

 weight of the stem of the brain and cerebellum to the whole 

 brain should be as 1 to 8. In the case of the idiot, the 

 imbecile, and the dement the proportion is much lower, viz. 1 

 to 6 or even less. In the idiot and imbecile the superficial area 

 of grey matter is greatly diminished; in the dement the grey 

 matter is wasted and destroyed. Not only do we see these 

 obvious defects, but if we compare the microscopic appearances 

 of a section of the normal brain, stained so as to show the cell 

 and fibre architecture, with a section of the brain of a congenital 

 feeble-minded person and the sections of the brain of a lunatic 

 who is demented or has lost his mind, we shall find in the case of 

 the ament born with deficient mind a deficiency of cells and 

 fibres in his cortex ; the superficial pyramidal cells which give 

 rise especially to the association fibres are poorly developed and 

 deficient in numbers ; the cells have but few branching processes 

 and are incomplete in their development, and there is not only, 

 as I have said before, a parallelism between the diminished 

 superficial extent of the cortical grey matter, but there is also a 

 parallelism between the depth of the mental deficiency and the 

 failure in numbers and development of the nerve cells and fibres. 

 Correspondingly, in the loss of mind of a chronic lunatic there 

 is a parallelism between the decay and atrophy of the cortical 

 grey matter and the degree of dementia ; the deeper the 

 dementia (loss of mind), the greater are the number of nerve 

 cells and fibres destroyed or undergoing decay and destruction 

 (fig. 3). I think then I have shown you sufficient evidence 

 to prove that the cortex cerebri is the material basis of mind. 



Causes of Mental Failure. — We must recognise the two great 

 groups of causes of mental deficiency or failure of the brain 

 to develop : (1) Germinal or gametic, an inborn failure of the 



