8o 



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 bei said to reach an extreme in the herbivorous mammalia; 

 and in many cases it is further increased by the independent 

 elaboration of the blind intescine 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- 

 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 

 DIVISIONS. ^^^ '^^^ 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 

 circum vallate 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. 



Fig. 41. The nasopharynx and related parts 

 of the head as seen in median section: i, tongue; 

 2, hyoid; 3, tonsil; 4, epiglottis; s, entrance to 

 trachea; 6, entrance to cesophagus; 7, basioccipital 

 bone; 8, soft palate; 9. pharnygeal aperture of 

 auditory (Eustachian) tube; 10, cranial cavity; 

 ir, ethmoturbinal scrolls; 12, nasal cavity; 13, 

 nasal septum; 14, hard palate; 15, oral cavity. 



