80 ANATOMY OF THE RABBIT. 
thus becomes extensively displaced to one side or other of the 
median plane. This development, while advanced in all mammals, 
may be said to reach an extreme in the herbivorous mammalia; 
and in many cases it is further increased by the independent 
elaboration of the blind intestine or caecum. In the rabbit the 
combined length of the small and large intestines is approximately 
eleven times that of the body. 
In considering the divisions of the digestive tube in the rabbit, 
the posterior, or post-cephalic portion, comprising the oesophagus 
and succeeding parts, may be distinguished from the anterior, or 
cephalic portion, the latter comprising the oral cavity and pharynx. 
The former is a free portion 
embracing the digestive tube 
proper, while the latter is a 
fixed portion exhibiting a 
variety of general mammalian 
features connected with the 
organization of the head. 
The form of the anterior, 
or cephalic portion of the 
digestive tube (Plate II) de- 

Fic. 41. The nasopharynx and related parts 
of the head as seen in median Section: 1, tongue; 
2, hyoid; 3, tonsil; 4, epiglottis; 5, entrance to 
trachea; 6, entrance to esophagus; 7, basioccipital 
bone; 8, soft palate; 9, pharnygeal aperture of 
auditory (Eustachian) tube; 10, cranial cavity; 
Ii, ethmoturbinal scrolls; 12, nasal cavity; 13, 
nasal septum; 14, hard palate; 15, oral cavity. 
pends on its fixed relation 
with respect to the enclosing 
parts of the head-skeleton. 
In the rabbit, as in mammals 
generally, the oral cavity is 
divisible into two portions, of which one is the oral cavity proper, 
while the other, the vestibulum oris, is a space enclosed between 
the alveolar process of the jaws and the teeth on 
the one hand and the cheeks and lips on the other. 
As in other vertebrates, the tongue is a muscular 
structure projecting upward and forward into the oral cavity from 
its base of attachment on the hyoid apparatus, but its greater 
elaboration, as well as the differentiation of special processes, the 
circumvallate and foliate papillae, for the accommodation of the 
gustatory organs, are features of mammalian significance. The 
roof of the oral cavity is formed by an extensive palatal surface, 
PRINCIPAL 
DIVISIONS. 
