INTRODUCTORY. 437 



the sphenoid, are inserted the temporal bones, a part of which 

 properly belong to the face. 



In the fostus the occipital bone is divided into four parts ; the 

 body of the sphenoid into two, and three of its pairs of alae are 

 separate. The temporal bone is divided into three, one of 

 which serves to complete the cranium, another to close the 

 labyrinth of the ear, and the third to form the sides of its cavity. 

 These parts of the bones of the cranium unite more or less 

 quickly in the different species, and end by perfect union in the 

 adult. 



The face is formed by two maxillary bones, between which 

 the nasal canal passes j they have the two intermaxillary bones 

 in front, and the two palatines behind ; between these descends 

 the single lamina of the ethmoid bone, called the Vomer. At 

 the entrance of the nasal canal, are the bones proper to the 

 nose. The jugal, or cheek bone of each side, unites the maxil- 

 lary bone to the temporal, and often to the frontal bones ; and 

 finally, the lachrymal occupies the internal angle of the orbit, 

 and sometimes a part of the cheek. 



The brain consists of two hemispheres, united by a medul- 

 lary lamina, called the corpus callosuni, contains two ventricles, 

 and inclosing four pair of tuherculce, or eminences ; these are 

 called the corpora striata, or striated bodies, thalami optici, or 

 optic beds, nates, and testes. Between the thalami optici is a 

 third ventricle, which communicates with a fourth, situated be- 

 neath the cerebellum. The crura of the cerebellum always 

 form under the medulla oblongata, a transverse prominence, 

 termed the tuber annulare. 



The eye, lodged invariably in its orbit, and protected by two 

 eyelids, and a vestige of a third, has its crystalline humour 

 fixed by the ciliary process. Its sclerotic coat is simply cel- 

 lular. 



In the ear there is always found a cavity, called the tympanum 

 or drum, closed from without by a membrane called the mem- 

 brana ttjmpani ; it has also four small bones, called the incus, 

 malleus, stapes, and os orbiculare, at the entrance of which is 

 placed the stapes, which communicates with three semicir- 

 cular canals ; finally, a spiral canal, called the cochlea, which 

 terminates by one of its canals in the tympanal cavity, and by 

 the other, in the vestibule. 



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