716 



SOLIPEDA. 



process, which encroaches largely upon the 

 squamous process of the temporal bone. The 

 zygomatic process of the temporal {Jig. 496. 

 o) has at its base a process which projects 

 upwards and backwards. This process con- 

 stitutes the entire length of the temporal 

 arch, articulating anteriorly by suture with 

 the post-orbital process of the os frontis 

 (fig. 495. b, c), which is very long : the zygo- 

 matic process of the temporal even extends 

 to beneath the orbit, the bony circle around 

 which it contributes to form, and is thence 

 prolonged behind the os malce, so as to be- 

 come articulated with the superior maxillary 

 bone. The occipital suture is situated con- 

 siderably in front of the superior occipital 

 ridge ; nevertheless there is generally an in- 

 terparietal bone of quadrangular shape, called 

 by hippotomists the os quadratum, but which 

 at an early age becomes consolidated with the 

 two parietals. The interparietal is, indeed, 

 itself frequently divided into two pieces in 

 the new-born foal. It is always much too 

 narrow to reach as far as the temporals. 



The anterior sphenoid appears but very 

 slightly in the orbit. The posterior sphenoid 

 mounts upwards in that region almost as high 

 as the temporal, but without coming in con- 

 tact with the parietal. Inferiorly, it is pro- 

 longed in a square form considerably beyond 

 the pterygoid region. The glenoid cavity for 

 the articulation of the lower jaw is situated 

 beneath the middle of the temporal arch ; it 

 is convex inferiorly, and has a tubercle situ- 

 ated behind its internal extremity, behind 

 which, and on the same level, is situated the 

 meatus auditorius externus. The bony meatus 

 remains distinct from the temporal even when 

 it has become completely consolidated with 

 the tympanic and petrous portions of that 

 bone. The tympanum is but little prominent, 

 and of a very irregular shape. The petrous 

 portion appears externally at the side of the 

 occiput (fig. 495. u), in front of the base of 

 the para-mastoid apophysis (fig. 495.jt?),which 

 is here long and pointed. 



Of the bones of the face it may be ob- 

 served, that the ascending apophyses of the 

 intermaxillary bones (fig. 495. 15) are placed 

 very obliquely, and become connected \\ith 

 the ossa nasi at about one third of the length 

 of those bones from their anterior extremity. 

 Inferiorly, their palatine apophyses penetrate 

 between the maxillary bones as far as the first 

 molar teeth, leaving two incisive foramina, or 

 rather fissures, which are about half the 

 length of the apophyses themselves. The 

 pointed extremities of the ossa nasi arch over 

 the cavity of the nose nearly as far as the 

 middle of the intermaxillary bones. Supe- 

 riorly, the ossa nasi increase in breadth as 

 far as the inner angles of the orbits, where 

 they become joined with the lacrymals (3, 

 4,5,6), which descend to a considerable dis- 

 tance upon the cheek, and enter almost as 

 largely into the structure of the orbital 

 cavity. The jugal (fig. 495. 7, 8) advances 

 upon the cheek as far forwards as the lacry- 

 mal bone, and terminates beneath the middle 



of the orbit. This bone does not extend 

 sufficiently far backwards to enter into the 

 composition of the zygomatic arch, properly 

 so called. It forms upon the side of the 

 cheek, by its union with the maxillary bone, 

 a broad, square ridge, which is continued 

 backward as far as the commencement of the 

 zygomatic arch* 



The palatine bone is deeply notched and 

 very narrow, not extending forward beyond 

 the penultimate molar tooth. This bone 

 merely forms a narrow border around the 

 meso-pterygoid fossa, but it composes more 

 than two thirds of the pterygoid alae. In 

 the floor of the orbit it mounts upwards, 

 between the maxillary bone on one side, 

 and the two sphenoids on the other, as far 

 as the os frontis, but it does not come in 

 contact with the lachrymal. The external 

 pterygoid process of the sphenoid runs along 

 the palatine externally, and extends beyond 

 it, but the internal pterygoid process is dis- 

 tinct from the sphenoid, forming a long and 

 narrow tongue-like process, which, after 

 having covered the lateral suture of the an- 

 terior end of the posterior sphenoid, extends 

 obliquely over the centre of the pterygoid 

 process of the palatine, and proceeds to form 

 a bony hook, situated upon the side of the 

 great palatine fissure. 



Spinal column. The cervical vertebra of the 

 horse are, as in all mammiferous quadrupeds, 

 seven in number; their proportions are mas- 

 sive, and the whole series forms a chain of great 

 strength and considerable flexibility. All the 

 posterior vertebrae of the neck have in the 

 horse a square or oblong shape, and both the 

 spinous and transverse processes are short 

 and stunted^ so as not to interfere with that 

 freedom and extent of motion which is essen- 

 tial in this portion of the spine. 



The atlas, as in man and other mammifera, 

 presents characters peculiar to itself. The 

 body of this bone is entirely suppressed, its 

 place being supplied by the two articulating 

 surfaces appropriated to the reception of the 

 condyles of the occipital : the superior lamina 

 are broad and flat, and the superior spinous 

 apophysis is not developed ; whilst, instead of 

 transverse processes, the vertebra is prolonged 

 laterally into two broad ala3, into which nu- 

 merous muscles are implanted. In the horse 

 it may be remarked that the entrance of the 

 canals for the passage of the vertebral arteries, 

 instead of being situated at the posterior 

 edge of the transverse apophyses, is placed 

 upon its upper surface, but in other respects 

 this bone presents no peculiarity worthy of 

 special notice. 



Axis. The configuration of the second 

 cervical vertebra in most quadrupeds differs 

 considerably from what is met with in the 

 human subject, owing to the horizontal direc- 

 tion of the neck, and the unfavourable posi- 

 tion in which the head has to be sustained. 

 This difference is most remarkable in the 

 arrangement of the spinous process, which, 

 instead of being merely a prominent tubercle, 

 as in man, is prolonged into a vertical crest that 



