of Edinburgh, Session 1873-74. 243 
The charcoal which remains in the stems renders their minute 
internal structure singularly distinct when a thin transparent 
slice is placed before the microscope. Longitudinal woody 
bundles, transverse medullary rays, crowded cells of the longitudinal 
fibres cut crosswise, are all seen most characteristically ; and in 
one specimen two inches in breadth the boundaries and whole 
structure of five annual layers of wood are displayed characteristi- 
cally, even to the naked eye. On the polished surface of one of 
the great stems, too, the eye can easily trace many annual rings for 
long distances. 
2. On a Method of Demonstrating the Delations of the Con- 
volutions of the Brain to the Surface of the Head. By 
Professor Turner. 
The outer surface of the skull does not correspond in shape to 
the outside of the brain. If it had corresponded there would 
have been no difficulty in determining the form of the brain from 
an inspection of the form of the head. 
The shape of the brain does correspond to the wall of the cranial 
cavity. This wall is formed by the inner table of the cranial 
bones, which table, though separated from the brain itself by the 
cerebral membranes, is moulded upon the exterior of the organ. 
The difference between the form of the inner table of the skull 
and that of the outside of the cranium is owing to the superaddition 
of the diploe and of the outer table, which superadded parts modify 
the shape of the outer surface of the skull. 
The diploe varies somewhat in thickness in different bones, or 
in different parts of the same bone, and even at different periods 
of life, and these variations necessarily cause the outer table to 
be removed to a greater distance from the inner table in some 
parts of the cranial wall than in others. 
The outer table is modified in shape by ridges and processes for 
the attachment of muscles ; e.g., temporal ridge, curved lines of 
occiput, occipital protuberance, mastoid process; but in certain 
localities, as the superciliary ridges, glabella and mastoid processes, 
more especially in the male skull, it is still further modified by the 
hollowing out of the diploe into the frontal and mastoid air cells 
