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93

The skull.

The skull of the Indian Elephant.

94

of the length of the last molar is in wear, the tooth has proceeded
so far forwards, that the posterior end of the proc. molaris is not
filled by the tooth. Its place has been occupied by a large air-
sinus (PI. 41 fig. 8), which opens into the neighbouring sinuses. The
proc. mol. thus persists also in the oldest Elephants, but its posterior
part is here not occupied by a tooth.

The pit on the hind end of the lamina pterygoidea mentioned
o above, which is present in many Mammals, is also present in the
Elephant, but is certainly not strongly marked; yet there is a
distinct hamulus pterygoideus and a crest ascending from it, while
the exterior limit of the pit is very feebly indicated.

It is not without interest to se how another Mammal with
especially mightily developed grinders has "arranged" itself.

In Hydrochoerus (PI. 34 fig. 10), where we find perhaps the
most powerful molar system next to that of the Elephant, the
maxillary bone with the enormous posterior alveolus also extends
backwards. But here it takes a more lateral position, does not
approach the middle line of the skull, does not either enter the
small alisphenoid canal and is posteriorly connected with an
anterior outgrowth from the squamosal, which lies on the lateral
side of the alisphenoid canal; the posterior end of the maxillare
in this manner receives a firm support. And as to the pit on the
hind face of the lamina pteryg. it is not at all as in the Elephant
levelled but on the contrary it has been deepened out to a large
and deep excavation inside the bon}^ wall of the last molar and
extending so far mediad, upwards and forwards that the presphe-
noid between the two excavations is reduced to a thin translucent
lamella. In this excavation the musculi pterygoidei, internus and
externus, take their origin.

The bony nasal cavity can in many Mammals be said to
lie horizontally, the ventral wall, the hard palate, parallel to the
basis cranii. Thus in the Dog and many others. Often however
are found deviations, for instance in the Ruminants the anterior
end of the hard palate is directed strongly downwards, if the skull
is held so that the basis cranii is horizontal.

In quite young Elephants (PI. 18) the deviation from what
we find in the dog a. o. is smaller than later on. Yet in the newborn
Elephant the hard palate, in comparison with the basis cranii,
rises from behind forwards c. 30°; and the nasal cavity is thus
a little oblique. Towards the outer bony nares it is however more
raised, in consequence of the dental part of the intermaxillary being
so much heightened; while the posterior part of the nasal
cavity is almost horizontal, the anterior part is rather oblique. In
this manner we find it in the quite young specimens.

In the course of years this is rather substantially altered. The
hard palate is in the new-born Elephant a rather thin plate as in
most Mammals. But already in the one year old Elephant that
part of it, which is situated immediately behind (below) the hind
end of the fissura palatina, is thickened, and by and by (comp.
PI. 19, 20, 27 etc.) this thickening, which evenly diminishes backwards
, becomes so considerable, that the longitudinal section of
the whole hard palate behind the fissura pal. in Chang forms a
triangle, the posterior leg of which is connected with the under
side of the palate at an angle of c. 60°; this line is the section
of the anterior side of the nasal passage, which has been considerably
raised also in its posterior part. Correspondingly, also
the opposite side of the nasal passage, that is formed by the
extraordinarily thickened presphenoid and basisphenoid, forms a
wall parallel to the inner side of the hard palate. The superior
part of the nasal cavity lying behind the rising part of the intermaxillary
, which has reached a mighty development, forms an even
continuation of the inferior part.

In this manner the "vertical" nasal cavity of the Elephant
comes into existence.

Also as to the position of the outer bony nasal aperture a
change takes place from the condition in the young Elephant to
that found in the old — a change, which also to a certain degree
contributes to the nasal cavity's getting a vertical position.

In the skull c the posterior border of the exterior nares is
situated nearly on the same cross-line as the end of the post-
orbital processus. In the skull / it has been drawn obviously

further back, being situated at a considerable distance behind a
cross-line through the postorbital processes. Still more this is the
case for instance in the skull k. But in the old Elephant Chang
(PI. 23 fig. 6) it has been pulled far back above the temporal
groove, far behind the line between the postorbital processes,
which are here situated above the anterior part of the nasal opening
; and the orbits, which in the young specimens are placed
lateral to the nasal openings, are in Chang lying almost wholly
before them1.

For the elephantine skull it is particularly characteristic and
peculiar that the growth from the }^oung age to the old quite
essentially takes place in the height of the skull, while the longitudinal
growth is relatively insignificant.

If for instance we compare the longitudinal sections represented
in the Plates 18—20 of the head respectively of a newborn
Elephant, of an Elephant seven years old, and of one c. fifty
years old, we find that the hard palate of the first is 16 cm long,
of the second 26J cm and of the old 50 cm long; in the course
of 7 years it has become somewhat more than \\ time as long
as in the new-born, in the course of 50 years 3 times as long
as in the new-born. During the same periods the height of the
hard palate reckoned unto the highest point of the intermaxillary
has respectively been doubled and become 5—6 times as great as
in the new-born; and if we take only the height of the palate unto
the hind end of the fissura palatina, the height of the seven years
old specimen is 3—4 times that of the new-born, and in the fifty
years old 12 times. In the old specimen the longitudinal section
of the palate behind and below the fissura palatina is an isosceles
triangle, in which the lower leg is c. 34, the other legs c. 24 cm long.

But still stranger are the conditions of the brain-case proper.
In the new-born the upper cranial wall has unto the end of the
nasal bone a length of 20 cm, in the seven years old a length of
26 cm, it has thus increased 30 %; in the old Elephant it is 42|
cm, has consequently only become a little more than twice as long
as in the new-born. During the same periods this same cranial
wall has in the place where it is lowest from 1 cm in the newborn
become respectively 6J and 22J cm thick: in the old Elephant
it is more than twenty times as thick as in the new-born,
while the length is only doubled. Exceedingly strange is also
what we find as to the basis cranii; it grows in length from 17
cm in the new-born to only 20 cm in the seven vears old and



Upper cranial wall
unto the tip of nasals

Basis cranii

Hard palate



Length

Height

Length
unto
the nasal
septum

Height
of the
basisphenoid
Length

Height
unto the

fissura
palatina

Height
unto the

highest
point of

intermaxillary
New-born, cm ...

20

1

17

3V2

16

1V2

6V2

7 years old, cm ..

26

6VS

20

6

26V2

5

13

50 years old, cm.

42i/2

22i/2

241/s

20

50

19

36

to 24| cm in the fifty years old specimen, an increase in 50 years
of only 44 % — while in the same periods the height from 3|
in the new-born increases to 6 in the specimen of seven years
and to 20 in that of 50 years, that is 470 %.

This singular check of the longitudinal growth of the elephantine
skull is likely an adjustment to the Elephants having
to carry the mighty tusks and the long rather weighty trunk at
the anterior end of the head. If the hind part of the head were
long, the muscular apparatus, which raises the head, should be
even much more enormous than it is.

An adjustment in the same direction is presumably also this,
that the brain of the Elephant is uncommonly short in comparison
with its breadth.

1 Comp. also the whole series of figures on the Plates 22—23. If in any of them
the figure does not agree exactly with the description as to the place of the hind
margin of the nares relatively to the postorbital processes, it is because, by the chosen
position of the skulls, what appears as the posterior margin of the nares is not this,
that margin lying truly somewhat more posteriorly. But nevertheless the series of
figures gives a fair account of the remarkable caudad wandering of the nares according
as the animal grows older.