134 OUTLINES OF EQUINE ANATOMY. 



margin to which the thyro-hyoid ligament and muscle are 

 attached. To their outer surface posteriorly is attached 

 hyo-thyro-pharyngeus a constrictor of the pharynx. 

 The spur and heel processes are connected together 

 by the body of the hone, which presents two surfaces and 

 four borders. To the 'posterior border hyo-epig'lottideus 

 runs from the base of the epiglottis, and the thyro-hyoid 

 ligament is attached. From the anterior horder the spur 

 process projects. The lateral borders posteriorly give rise 

 to the heel processes, anteriorly present circular synovial 

 articulatory surfaces which look in a forward, upward, and 

 outward direction ; to these the inferior extremities of the 

 short cornua are attached. The superior surface of the body 

 and the upper sharpened border of the spur process afford 

 attachment to retractor lingualis, an obscure muscle, the 

 fibres of which, imbedded in the fatty substance of the 

 tongue, influence its movements. The inferior surface of the 

 body receives the superior terminal portions of suibscapulo- 

 hyoideus and sterno-thyro-hyoidens. The inferior sharp- 

 ened border of the spur process affords attachment to mylo- 

 hyoideus and its extremity, which is its deepest part, to 



Genio hyo-glossus, the muscle which lies in contact 

 with its fellow at the central plane of the tongue, and 

 which, being attached to this point and to the symphysis 

 of the inferior maxilla, sends fibres in a radiating direction 

 upwards to become lost in the musculo-adipose matter of 

 the tongue as far forward as its tip. 



Genio -hyoideus also runs from the anterior extremity of 

 the spur process of the os hyoides. It becomes attached an- 

 teriorly to the symphysis of the jaw, and lies in contact with 

 its fellow in the central line of the inter-maxillary space. 



Extending in an oblique direction foi-wardsand upwards 

 from the synovial articulatory surfaces of the latera,l parts 

 of the body of the hyoid bone are the short cornua, cylin- 

 drical portions of bone shorter than the heel processes, 

 s-nallest at the centre, superiorly connected by fibro- carti- 

 lage {in which is generally to he found a bony nodule analo- 

 gous to the middle cornu of the ox) to the inferior extremity 

 of the long cornu. These are embedded in the base of the 

 tongue and are connected together by the 



Hyoideus transversus, which runs from the internal 

 surface of one short cornu to that of the other. 



Hyoglossus brevis, the fibres of this muscle arise from 



