TRANSACTIONS OF THE SECTIONS. 127 
they are formed upon a preceding plan. The gyri or convolutions have a known 
disposition, corresponding more or less on each side in all brains, so that it is possible 
to trace out on paper what course the convolutions of a healthy brain will take—at 
any rate, the exceptions will be in small particulars; and this not in man only, but 
more easily as we descend through the inferior forms—the savage, the idiot, the 
chimpanzee, the monkey, the carnivora, and so on. 
That portion of the skull occupied by the cerebrum proper may be divided into 
five surfaces—an ethmoidal, lodging the olfactory lobes, small in man, but ample in 
other mammalia, as the marsupial or elephant; a sphenoidal, to which the grey 
matter about the optic commissure and the island of Reil correspond; a frontal 
for the anterior lobes of the brain, temporal-surfaces for its inferior tuberosities; a 
parietal for the vastly predominant superior middle portion; and an interparietal, 
corresponding to the posterior lobes. 
Wishing to see exactly what gyri or sulci correspond to the sutures which divide 
the regions of the skull, and finding that this cannot by ordinary comparison be 
well done (our present modes of examination giving us anything but clear ideas of 
the topography of the encephalon), the author devised a plan of piercing the skull 
along the sutures, and marking the corresponding points of the brain by vermilion 
introduced by means of a grooved needle. He then extracts the brain, and lets it 
fall into a strong solution of corrosive sublimate, which has the effect of rapidly 
hardening it so that it will allow of a perfect cast being taken from it. The mem- 
branes may also be easily removed, though with more difficulty over the posterior 
lobes. Pins are introduced into the brain at the spots where the vermilion punc- 
tures are seen previous to taking the mould, which should be formed of two appli- 
cations of the liquid plaster, the first most fluid and of little bulk. 
With respect to the coronal suture, which appears to trend backwards in the 
greatest deeree in the lower races of man, it will be found to correspond to a certain 
describable line. This begins before the first convolution above the commencement 
of the fissure of Sylvius, and rises, not along the oblique fissure of Rolando (sepa- 
rating the first from the second of those three remarkable oblique convolutions 
arising from the upper lip of the Sylvian fissure, and going upwards and backwards 
to the vertex), but more directly upwards, and more in front, before the anastomoses 
which the anterior oblique convolution has with the frontal ones. These frontal 
convolutions evidently run in a longitudinal direction in the adult, but more 
evidently so in the foetal brain, well marking the frontal portion. Within the 
longitudinal fissure the separation of the frontal and parietal portions is commonly 
well marked in man, monkeys, and the lower mammalia. 
The squamous suture corresponds to the fissure of Sylvius, which, as far as the 
external surface of the brain is concerned, may be said to commence about the 
summit of the great ala of the sphenoidal bone, which in some skulls (prognathous 
ones) does not always reach to the parietal bone. 
A suture occasionally exists in the occipital bone, marking the posterior edge of 
the brain, apparently common in the American races, but not peculiar to them, as 
was seen from photographs of a Negrito and other skulls, illustrating the paper in 
this and other points relating to the skull, and kindly lent by Dr. J. Barnard Davis. 
This interparietal bone (the cerebral portion of the occipital) appears to be worthy 
of study; it is large in the inferior races of man, and also full in the female. The 
lambdoidal suture corresponds to the line which divides the conyolutions forming 
the third lobe from the middle or parietal—a line commonly well marked on the 
brain surface, though not an uninterrupted sulcus; more strongly in the Quadru- 
mana, but still more strongly internally in the longitudinal fissure. The inferior 
tuberosity of the brain is most intimately connected with the posterior lobe. 
The parietal portion of the upper surface of the brain constitutes, of course, by far 
its largest region. Before, are some gyri already mentioned as being anastomoses 
of the anterior oblique parietal convolution with the frontal. These anastomoses, 
in combination with the inner frontal convolution, form in man a broadly halberd- 
shaped figure, the coronal suture crossing at a little distance before the handle as it 
were, but in many mammalia a broader trilobed figure like a club of cards or a fleur- 
de-lis, Behind, we have already described three more or less well-marked conyolu- 
tions going from the fissure of Sylvius upwards and backwards to the middle line, 
