64 
A TREATISE ON ELEPHANTS. 
which separate the outer from the inner table of the skull ; the 
structure is so disposed as to afford great strength with little material. 
During early life these cavities are small, but with age they increase 
greatly. 
The nasal bones are short, triangular, and pneumatic, forming 
the lump or boss seen immediately above the root of the trunk. 
The cavities or sinuses are broken up into numerous subdivisions by 
irregular partitions, and are lined with a delicate membrane ; they 
communicate freely with one another and with the nasal cavities, and 
while their aggregate bulk constitutes a very considerable portion 
of the skull, so very thin and light are they, that if a section be 
made of that portion of the head which includes the greater portion 
of them, it will be found to weigh from 8 to 1 1 lbs., whereas 
that of the entire skull often exceeds loo lbs. in weight. The 
average weight of five skulls of male elephants was found to be 
I i4f lbs. ; one of these, however, was an exceptionally large head, 
weighing 1754 lbs., i.e.^ upper jaw 59 lbs., lower jaw 1164 lbs. 
Owing to the peculiar structure of the skull referred to, a large 
extent of bony surface is provided for the attachment of muscles, 
without materially adding to the weight of the head, and by 
means of the air contained in the sinuses the skull is rendered 
buoyant, the animal being thus enabled to support the enormous 
weight of the teeth and lower jaw. The large amount of 
cell structure interposed between the outer and inner tables 
of the skull affords such an important organ as the brain great 
protection. 
The bony nostrils are formed by the nasal and premaxillary bones ; 
the nasal chambers are very short and vertical. The turbinal bones 
situated within the nasal aperture are rudimentary, and it is here 
that we find the apertures admitting air into the extensive air 
chambers of the skull. 
The lachrymal bone is small, protuberant, and imperforate. 
The cavity in which the brain is lodged is situated low and far 
back. The brain is oval in shape [see Fig. 31), and the division 
between the large and small brain is vertical, i.e.^ they lie on a level 
plane without overlapping. The olfactory lobes from which the 
nerves of smell proceed are large, whilst the nerve of sight and 
muscular nerves of the muscles of the eye are singularly small for so 
vast an animal ; and one is immediately struck by the prodigious 
size of the nerve which supplies the proboscis with its exquisite 
sensibility, as well as by the great size of the motor portion of the 
nerve which supplies the same organ with its power of movement 
and action.^' — [Emersofi Tennent.) In animals of ordinary size 
the brain weighs from 15 to 17 lbs. 
