STRUCTURE OF THE CORTEX CEREBRI. 
55 
and size according to their local distribution. Thus the cells found in that portion of 
the parietal lobe dipping into the crucial sulcus are peculiarly swollen, globose, and of 
Fig. 5. 
great size—-frequently solitary, or arranged in twos or threes. The cells of the limbic 
portion of this sulcus are, on the other hand, smaller, elongated, and thickly grouped. 
In front of the crucial sulcus the whole cortex of the limbic lobe is distinctly modelled 
upon the five-laminated plan, fig. 5. Posterior to the crucial sulcus the small pyramidal 
and angular cells begin to congregate towards the lower confines of the third layer, 
and this tendency increases from before backwards, so that towards the posterior end 
of the corpus callosum these small elements form a distinct layer above the ganglionic 
series. This six-laminated structure is maintained backwards as far as the retro-limbic 
annectant, which is also modelled upon the same type. Tracing the five-laminated 
Fig. 6. 
Fig. 7. 
type beyond the confines of the limbic lobe, we find it extends through the wdiole of 
the frontal lobe, and that it is limited externally by the fissure of Rdlando. In the 
anterior part of the Sylvian convolution we meet with a transitional form of lamina¬ 
tion, whilst a more purely five-laminated cortex occupies the anterior extremities of 
the third and fourth parietal convolutions. The latter or sagittal convolution in the 
neighbourhood of the crucial sulcus shows an especially rich development of the five- 
laminated cortex and its clusters of ganglionic cells. 
Relative Area of Five-laminated Cortex in different Animals. 
When inquiring into the architecture of the human cortex cerebri, it was stated 
that the five-laminated cortex, conjoined to the clustered arrangement of ganglion 
