314 RESEARCHES ON CORTICAL LOCALISATION AND 



are compounded in the human mind, into harmonious series of 

 concepts by means of voluntary attention and selection, is only 

 limited by the degree of functional development of this lobe in any 

 particular individual of the race. The lower associational centres 

 of man, which represent the physical basis of the content of mind, 

 are thus co-ordinate in development with the centre of higher 

 association and co-ordination, which represents the physical basis 

 oi the capacity to voluntarily group into a harmonious and con- 

 nected sequence the higher psychic units of the mind. 



Passing now from the highest to one of the lowest orders of 

 mammals, namely, the insectivora, one may obtain histological 

 evidence of equal importance with regard to the functions of the 

 cerebrum. Watson, in his recent paper, has mapped out the 

 minute brains of certain members of this order into histologically 

 different regions. Certain of these areas he regards as centres 

 of projection, and another, on the dorsal and mesial aspect, he 

 designates ^ motor " from its histological structure. The re- 

 mainder of the cortex, from the embryonic appearance of the 

 cells contained in it, he designates " undifferentiated." The 

 conclusions of Watson with regard to his investigation are best 

 expressed in his own words : 



" It seems necessary to assume that animals like the mole are 

 possessed of some means of simple sensory association, otherwise it 

 is probable that. the animal's waking life would tend to be one of 

 almost continuous sensory confusion. Such association is called up 

 by the stimulation of one or other or more than one special sense, 

 and passes more or less directly to a motor or efferent result. This 

 appears to be the lowest grade of conscious neopallial association 

 i.e. of psychic function and it doubtless persists in mammals much 

 higher in the scale than the insectivora, and possibly in the highest, 

 though obscured in them by the development of a higher grade or 

 grades. It is not likely to exist as a random passing to and fro of 

 impulses from this sensory area to that, but to lie in some fusion zone. 

 Careful examination of the cortex of animals like the mole has failed 

 to reveal any attempt at the development of a ' psychic ' zone in 

 direct relation to any of the sensory projection spheres. The writer 

 does not consider that on histological grounds one is justified in 

 drawing close analogies between the areas he has termed ' undif- 

 ferentiated ' in the mole, &c., and the areas of cortex surrounding 

 the projection spheres in certain higher mammals. From the histo- 



