268 



ANATOMY OF VEIlTEBliATES. 



fangs : when tliey are of limited growth, and usually molars : ever- 

 groAving teeth require the base to be kept open for the persistent 

 pulp. Some Mammals are ' monophyodont/ ^ or have but one set 

 of teeth: the majority are ^ diphyodont/ ^ or have two sets: none 

 have more. The tongue is large, fleshy, mth the apex more or 

 less free. The posterior nares are protected by a soft palate, and 

 the larynx by an epiglottis, fig. 139, ep : the rings of the trachea 

 are generally cartilaginous and incomplete behind : there is no 

 inferior larynx. The oesophagus, ib. cc, is continued without 



partial dilatations to the 

 ^"^^ stomach, ib. g, which va- 



ries in its structure accord- 

 ing to the nature of the 

 food, or the quantity of 

 nutriment to be extracted 

 therefrom. 



The vertebral bodies, 

 fig. 141, c, are ossified 

 from three centres, and 

 present for a longer or 

 shorter period of life a 

 discoid epiphysis at each 

 extremity. They are ar- 

 ticulated by concentric li- 

 gaments with interposed 

 glairy fluid, fig. 199, form- 

 ing what are called the 

 intervertebral substances ; the articulating surfaces are generally 

 flattened, but, in the neck of certain Ungulates, they are con- 

 cave behind and convex in front. The cervical vertebrae, in all 

 Mammals save two, are seven in number, neither more nor less. 

 The atlas is articulated by concave zygapophyses to two convex 

 condyles, which are developed from the neurapophyses (exocci- 

 pitals) of the last cranial vertebra. 



The scapula is generally an expanded plate of bone ; the cora- 

 coid, with two (monotrematous) exceptions, appears as a small 

 process of the scapula. The sternum is usually narrow, and con- 

 sists of a simple longitudinal series of bones : the sternal ribs are 

 generally cartilaginous. The centrums of two cranial vertebras 

 (basisphenoid and prcsphenoid) preserve their distinctness to a 

 late period of growth, in the species where they ultimately 

 coalesce. 



' jji.6vos, once; 



Mammalian vertebra, lumbar of Wlaale. 



(pvu, I generate; oZovs, tooth. 



- Sfs, twice; <pvu>, and ohovs. 



