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Proceedings of the Royal Society of Edinburgh. [Sess* 
Bolton (34, 35), in two papers — one on the histological basis of amentia 
and dementia, the other on the function of the frontal lobes — gives the 
conclusions arrived at by him on the functions of the various portions of 
the cortex cerebri. He concludes that the prefrontal region is the centre 
for the highest co-ordinated and associated processes of the mind. From 
examination made by him of human foetuses of four and six months, he 
finds that lamination begins in the cerebral cortex at the sixth month of 
foetal life. At this stage he finds the polymorphic layer almost fully 
formed, the granular layer about half its full size, while the pyramidal 
layer is barely a fourth of its full depth. He finds that the pyramidal 
layer develops enormously up to and after birth. From this, and 
from the fact that in mental diseases the pyramidal layer invariably 
degenerates, he concludes that this layer subserves the psychic or 
associative functions. The polymorphic layer is never found to have 
undergone change in mental disease, and, as already stated, it is practically 
fully developed at birth; it evidently subserves the voluntary or lower 
animal functions. The granular layer apparently subserves the trans- 
ference of afferent impulses from sense organs to other parts of the 
brain. 
Miss Allan (37) describes a series of experiments made to test the 
psychical processes peculiar to the guinea-pig, and the changes occurring in 
those processes from birth to maturity. As a result of these experiments. 
Miss Allan finds that there is no evidence of an increase in the complexity 
of psychical processes after the third day of life. It also seemed evident 
that the memory of a particular set of movements — such as would be 
required to retrace a labyrinth to find food — is registered by the kinsesthetic 
sense. At birth nerve medullation is found to be far advanced, its 
completion occurring in a few weeks. An interesting comparison is made 
between the conditions found in the guinea-pig and in the white rat, as 
described by Watson (36). In the latter animal none of the nerve fibres 
are medullated at birth, while the animal is quite helpless. This is in 
sharp contrast to the newly born guinea-pig, who starts life with its 
psychical powers almost mature. The psychical maturity of the white rat 
is reached about the twenty-seventh day after birth, but is far in advance 
of that found in the guinea-pig. 
Edinger (38) contributes an interesting description of the brain of the 
lamprey. The prominence of the olfactory bulb and its structure are 
minutely described. 
Watson (39), in a paper on the mammalian cerebral cortex, describes 
minutely the brains of the mole, shrew, and hedgehog, and defines the 
