BIOLOGY: -
ANATOMY -
INTERNAL ANATOMY:
Rotating View of the Brain
.
.
On
this page, a rotational view of the thylacine brain (endocranial cast)
is shown. An endocranial cast (endocast) is usually created by pouring
a quantity of moulding material such as siliconized latex into a skull's
cranial cavity to form a coating on the inner surface. After the
material cures, the resulting flexible impression (which is a hollow membrane)
is then extracted back through the foramen magnum (the large hole at the
base of the skull which allows passage of the spinal cord). The hollow
inside of the mould is then filled with plaster to maintain its inflated
shape. In mammals, endocasts look remarkably brain-like, resembling
an intact brain with the dura
mater in place. This thylacine endocast was made by Professor
Heinz Moeller in the late 1960s.
.
.
Courtesy:
Nicholas Ayliffe (ITSD Project).
Occasionally, endocasts
are formed naturally. This occurs when sediment such as sand or mud
is washed into a skull's cranial cavity prior to fossilization, and then
becomes fossilized along with the skull itself. Millions of years
later, when earth movements eventually expose the complete fossil skull,
weathering occurs which destroys most of the bone but leaves behind the
natural endocast since it is made of a harder material that is more resistant
to weathering. Well known examples of natural endocasts include those
of the Late Eocene mammal Bathygenys
reevesi.
