1879.] 



Comparative Structure of the Cortex Cerebri. 



237 



important part in the explication of fundamental divergencies in the 

 role of cerebral activity — tbns, close concentrated association of 

 centres is maintained in those animals where the associated move- 

 ments of vast mnscnlatnres are required to act in concert for sudden 

 and supreme efforts in the struggle for existence — hence the peculiar 

 structure of the motor area m the cat and ocelot. 



The dissociation observed in man and the ape appears to point to 

 the comparative independence of special musculatures, to the possi- 

 bility of their higher education, and (in the great disproportionate 

 complexity of certain areas) to the pre-eminently high and complex 

 relationships of these special centres and the musculatures which they 

 represent. 



The widespread dissociation of centres observed in the species of 

 Ungulata examined, points, on the other hand, to a comparative sim- 

 plicity in their resultant activities — there being in these animals no 

 special demand for the collective and complex associations in action of 

 widely separated musculatures. 



13th. The results of the investigation lend still stronger confirma- 

 tion to the belief that these anatomical units of the ganglionic layer 

 are especially concerned in the production of those complex move- 

 ments, which Ferrier has shown to be the special functional endow- 

 ment of the motor area ; and it is highly probable that a study of the 

 dimensions, distribution, and relationships of these cells in the lower 

 animals will serve to elucidate, in some degree, the diversified phe- 

 nomena resulting from the excitation of this important area of the 

 cerebral cortex. 



Note. — -In a recent contribution (" Psychiatrisches Centralblatt," Nr. 6), 

 Meynert, referring to the discovery by Betz of the pyramidal cells in the motor area, 

 attributes to it no importance. He states that the size of these cells depends simply 

 upon the distance pursued by their processes towards the outer zone of the cortex. 

 I need scarcely point out the self-evident fallacies involved in this fine of argument. 

 Suffice it to say, that such a rule cannot be one of universal applicability, since, 

 although the size of these cells as a general fact increases with their depth, yet, 

 from the second down to the fourth layer, we find numerous pyramidal cells no 

 larger than those of the second layer. Again, over many regions of the cortex, the 

 cells of the third layer are often larger than those of the fourth. In these cases, 

 therefore, Meynert's assumption is untenable. Further, these cells are often larger 

 at the sides of a gyrus and the bottom of a sulcus than beneath the summit of the 

 convolution, i.e., at a shallower portion of the cortex than at a deeper site. As this 

 theory of Meynert does not explain the very specialized form, relationships, or 

 arrangement of these elements, nor provide for the constant and extensive excep- 

 tions to be taken to his rule, the above considerations, together with others which 

 must occur to a candid and careful inquirer, will prove wholly subversive of such a 

 doctrine. 



