H. W. MAGOUN 5 



science the results of the operation of mental powers which in the lower 

 animals are purely nistinctive and in the lowest organisms simply vital 

 processes.' 



There can also be found in Laycock an expression of the conflicting 

 interests of the different levels with the higher holding the lower in check, 

 to be elaborated later by Jackson and by Freud: 'This entire group of 

 corporeal appetites and animal instincts is characterized by the quality of 

 necessity. They are imperative on the individual; in lower organisms they 

 are performed blindly. In man and higher vertebrates, in whom there is a 

 development of cognitive faculties, they may be made to act as a check 

 upon each other and thus states of consciousness, termed motives, will 

 coincide with a knowing restraint exercised over them. But even with the 

 highest and strongest of human motives, it is often found difficult to curb 

 them effectually. The entire group constitutes "the Flesh" of St Paul. 

 Those classed under the head of primordial instincts or corporeal appetites, 

 most necessary to the well being and maintenance of the organism anci the 

 species, are the farthest removed from the will and consciousness.' 



His clinical observations in neurology led Laycock to consider disease 

 as 'retrocession', in which changes taking place were the inverse of evolu- 

 tionary. He proposed a law of 'disvolution in certain kinds of brain 

 disease, when there was a decay of the mental powers and return to an 

 earlier, infantile status. Concepts of evolutionary levels of function, con- 

 flicting in their interests and exhibiting dissolution in neurological disease, 

 can thus be detected in a germinal stage in Laycock's views. 



Jaekson's psychological concepts were strongly influenced by Herbert 

 Spencer, from whom Darwin borrowed the term 'survival of the fittest'. 

 After having been an evolutionist for some time, in 1851 Spencer formu- 

 lated the basic principles that were to be elaborated in most of his later 

 work. He had been asked to write a notice of a new edition of Carpenter's 

 Principles oj Physiology and 'in the course', he noted (1904), 'of such perusal 

 as was needed to give an account of its contents', came across the theory of 

 von Baer — that the development of all plants and animals was from homo- 

 geneity to heterogeneity. This concept of progressive differentiation, 

 added to that of Lamarckian adaptation, became his distinctive evolu- 

 tionary principle. 



Having just turned forty, Spencer determined to devote the remainder 

 of his life to the systematic apphcation of this concept to the whole field 

 of knowledge. Flagging a dilatatory cerebral circulation, with which he 

 was hypochondriacally preoccupied, with bouts of exercise preceding 

 dictation to an amanuensis, Spencer embarked on the exposition of a 



