THE INTERNAL SKELETON. 18t 
bone (which articulates with the inner aspect of the quadrate) 
and the end of a quadrato-jugal bone (which articulates with 
the outer aspect of the quadrate). 
The median and inferior bar of bone is the most irregular 
in form and altogether the most inconstant of the six. It is 
formed of a bone, called the vomer, generally single, but which 
may be double (two side by side), extending from beneath the 
anterior part of the rostrum, forwards towaras the middle part 
of the premaxilla, with which it is often connected by soft 
tissue only. 
The two organs of smell are situated one on either side 
within the facial part of the skull, being sheltered and more or 
less protected by the bony framework of the bill. A scale- 
like bone, called the nasal, roofs over the hinder part of each 
nasal cavity, aud forms the hinder margin of the nasal aperture. 
This bone consists of a posterior body and two forwardly 
extending and diverging limbs, the angle between which may be 
more or less acute or may be rounded. When itis rounded, and 
a line, joining the most backward point of the margin of the 
nasal of one side with that of the other, passes in front of the 
hindmost end of the median backwardly extending branch of 
the premaxilla, such a nasal is called holorhinal, If the angle is 
acute, and the same transverse line does not pass in front of the 
hinder end of the median branch of the premaxilla, then such a 
nasal is called schizorhinal. Extending outwards on either side 
of the median, ascending branch or process of the premaxilla, 
external to each nasal, another bone called the lachrymal is 
placed at the front margin of the orbit. Within it is a bone, 
bounding the orbit in front, called the lateral ethmoid. The 
anterior part of the interorbital septum is called the median 
ethmoid. At the hinder margin of the orbit there is a more 
or less prominent process called the postfrontal. 
Returning to consider the cranium proper, or brain-case, it 
may be noted that the hole mentioned as permitting the 
junction of the brain and spinal marrow is called the foramen 
magnum. It isalso called the occipital foramen, because the most 
posterior region of the skull is called the “ occipital ” region. 
Immediately beneath the foramen magnum is a spheroidal pro- 
minence which fits into the depression on the front of the atlas 
vertebra already described. This prominence is called the oce?- 
pital condyle. The bones which enclose the internal ear are 
called pertotic, but they are not separate from the parts of the 
