OF ME NT A L NER VO US A CTION. 1 3 T 



as to constitute a mechanism (if this term may be properly 

 applied to it) of marvellous perfection and complexity. 

 The fibres, many being of extreme tenuity, are seen to 

 interlace with one another, and run in every conceivable 

 direction, so that when the observer realizes the actual 

 arrangement as it exists in a very small portion of grey 

 matter, and this is the utmost he can hope to do, he marvels 

 how it has been brought about. Though he is convinced 

 that the whole has been, as it were, laid down according to 

 a definite plan and has been designed to fulfil a special 

 purpose, he is unable to picture to himself the gradual 

 changes by which the result has been attained, and he 

 cannot discover the laws which have governed them. There 

 can, however, be no question that our knowledge upon these 

 matters will increase as investigation advances, although it 

 is not likely we shall ever be able to explain with exactness 

 the nature of the power, force, or property which determines 

 at the first the ultimate structure and exact arrangement the 

 mechanism shall at length acquire. To state that this is due 

 to crystallisation, or formifaction, or differentiation, and to 

 offer any such vague assertion as an explanation of the facts 

 observed, is not adding to our knowledge. 



After having shown (p. 87) in what particulars the for- 

 mation of the simplest structure differs from the process 

 of crystallisation, it is unnecessary to discuss the question 

 with reference to the highest and most complex tissue 

 known. But even if we could explain the formation of the 

 complex structure of the cerebral convolutions, we should 

 have advanced but a little way towards a knowledge of 

 mental action, for, as it were, behind all this structure, 



K 2 



