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to which the senses are liable, in the course of phylogeny. For instance, although the sense of 

 smell is to Man of minor importance, and the lobus pyriformis has dwindled down to a fraction of 

 its earlier representation its representation, let us say, in Sus yet, on making a microscopic 

 comparison of the lobe in the two animals, such a pronounced reproduction of the primitive 

 formation is observable, that a superficial inspection will fail to distinguish sections of one from the 

 other. And, in the case of all the other primary areas, a corresponding condition of affairs holds, 

 but to a graded extent; thus, from my examination of these areas, I should say that the structure 

 of the visual cortex stood next to the olfactory in stability, while the auditory and common sensory 

 cortex I should bracket together last. 



From this it appears that a proposition can be formulated to the following effect : the stability 

 of the architectural plan of any given field of cortex is directly related to the age of that cortex, 

 and to the importance, as a means to survival, of the function it subserves. The corollary to be 

 drawn from the foregoing proposition is that by utilising the discriminating powers of the micro- 

 scope it is possible to estimate and graduate, to a certain extent, the phylogenetic age of the 

 various functional territories. 



Contradictions assert themselves when we attempt to apply this rule to the history of the 

 motor cortex. One matter calling for explanation is that whereas in Carnivorae, Anthropoidea, and 

 Homo what we must regard as the principal element, the giant cell of Betz or ganglionic cell of 

 Bevan Lewis, is well represented, in the pig and other animals the same element is undeveloped. 

 In the case of Sus communis we might suppose, and not be altogether wrong in doing so, that the 

 particular cells to which I have drawn attention in the belief that they are homologous with the 

 motor cells of Homo, have undergone retrograde changes, that they are relatively small in size and 

 otherwise atypical, as a result, to some extent, of the confined life the species has been forced to 

 lead through countless generations. But the condition of affairs in the rabbit forces us to pause; 

 we are told that in the cortex of this animal not a single Betz cell is recognisable 1 , and yet hardly 

 any mammal makes fuller use of motor activity as a means to escape from its enemies. Contradic- 

 tions in nature such as this are, to say the least of them, puzzling, and apt to lead us away from 

 the truth : still, after giving the whole matter full consideration, and in spite of these contradictions, 

 there seems to me to be only one conclusion, and it is that the motor function is late in being 

 represented " re-represented," in Dr Hughlings Jackson's words in the upper or cortical level. 

 Pursuing this point further, we cannot doubt that the movements of all non-mammalian verte- 

 brates (Pisces, Amphibia, Reptilia, Aves), despite their activity, must necessarily be generated 

 in the spinal cord, probably coordinated by the well-developed cerebellum. Then, even among 

 mammals, it is as likely that there are many low down in the scale in which movement is either 

 not at all, or only indifferently, " re-represented " in the cortex cerebri. Such a supposition would 

 explain the locomotor activity of the rabbit. Ascending the scale we arrive at the condition 

 exemplified in the pig, where an advance in cortical representation is indicated by the deposition 

 of germinal elements, and so onwards through Carnivorae, Simiadae, and up to Homo, there occurs 

 a gradual perfection of the representation in both the physical and the psychic sense. Reasoning 

 inversely, the proposition is forced upon us, that since among the primary functions motion lags 

 behind in obtaining cerebral government, so the giant cells characterising motor cortex are com- 

 paratively late in being added to the pallium. 



So far one has written only of the fields of cortex dominating primary functions more or less 

 common to all vertebrata. A few remarks, comparative in nature, will now be offered on that 



1 Kolmer has made serial sections of the crucial region of the Bat, Hedgehog, Rabbit, Mouse, Eat, Guinea-pig, 

 Ox, and Pig, and states that not a single "motor" cell is to be found. It is evident, however, that in the case 

 of the Pig he has overlooked the elements I regard as the homologues of giant or motor cells, cells, by the way, 

 which Dr Bevan Lewis has also seen and figured (Text-book of Mental Diseases). 



c. 37 



