176 ANATOMY OF THE RABBIT. 
I. EXTERNAL FEATURES. 
The external structures, subdivisions of the body, and super- 
ficial skeletal points may be made out as follows. 
1. The division of the body into the head (caput), neck 
(collum), trunk (truncus), tail (cauda), and the anterior and 
posterior limbs or extremities (extremitates). 
2. In the head: 
(a) The division into a posterior, cranial portion (cranium), 
and an anterior, facial portion (facies). 
(b) The mouth (os), bounded by the cleft upper lip (labium 
superius) and the undivided lower lip (labium inferius). 
The large sensory hairs or vibrissae. 
(c) The nose (nasus), and its external apertures (nares an- 
teriores). 
(d) The eye (oculus), and its coverings, the eyelids, including 
the upper eyelid (palpebra superior), the lower eyelid 
(palpebra inferior), and the third eyelid (palpebra tertia). 
The third eyelid occupies the anterior angle of the eye, and 
is comparable to the conjunctival fold of the human eye. 
(e) The external ear (auricula), and its canal, the external 
acoustic meatus (meatus acusticus externus), leading to the 
tympanic membrane. 
(f) Points on the head skeleton, to be identified by feeling 
through the skin; zygomatic arch, supraorbital process, 
external occipital protuberance, angle of the mandible, 
symphysis of the mandible, and the hyoid bone. 
2. In the trunk: 
(a) The division into thorax, abdomen, and back, or dorsum. 
(b) The inclusion with the trunk of the proximal portions of the 
limbs. The angle formed by the anterior limb with the 
trunk represents in part the axillary fossa (fossa axillaris). 
The depression is much less evident than in man on account 
of the different positions of its enclosing folds formed by the 
pectorales and latissimus dorsi muscles. A corresponding 
inguinal furrow separates the posterior limb from the 
abdomen and pelvis. 
