170 THE ANATOMY OP THE HORSE. 



the antero-cxtcrnal foramen of the atlas, and dividing there into cerebro- 

 spinal and occipito-musndar branches. The former enters the spinal 

 canal by the antero-internal foramen ; the latter divides for the supply 

 of the muscles and other stnxctiires of the poll. 



The Retrograde or Anastomotic branch of the occipital artery will be 

 found issuing with a backward course from the posterior foramen of the 

 atlas, and inosculating with the termination of the vertebral artery. 



The Mastoid branch of the occipital artery will be found beneath 

 the obliquus capitis superior. It ascends behind the styloid process; 

 and crossing over the mastoid crest, immediately above the mastoid 

 process, it passes imder the edge of the squamous temporal bone, and 

 enters the parieto-temporal conduit, in which it anastomoses with the 

 spheno-spinous branch of the internal maxillary artery. 



Veins. — Satellite veins accompany these arteries. 



THE INTERMAXILLARY SPACE. 



Directions. — Incise the skin along the middle line, from the mental 

 symphysis upwards, and raise it on each side as far as the edges of the 

 rami. 



Cutaneous Nerves. The skin of the intermaxillary space is supplied 

 by a nerve derived from the 2nd cervical nerve. It comes from the first 

 stellate group of cutaneous nerves already seen on the surface of the 

 mastoido-humeralis ; and crossing obliquely downwards into the space 

 (the long axis of the head is supposed to be vertical), it extends to 

 near the symphysis of the lower jaw. 



The Panniculus. This is here extremely thin. It hardly forms a 

 continuous layer, but consists of muscular fasciculi scattered in an apon- 

 eurosis. 



The Submaxillary Lymphatic Glands (Plate 27). This group of 

 glands is placed on the inner side of the horizontal ramus, a little above 

 the point where its edge is crossed by the submaxillary vessels and 

 Stenson's duct. It rests on the lower belly of the digastricus muscle, 

 being related inwardly to the insertion of the subscapulo-hyoid mxiscle, 

 and outwardly to the submaxillary artery. The right and left groups 

 extend towards each other, and nearly meet below the extremity of 

 the glossal (spur) process of the hyoid bone. These glands are placed 

 on the track of the lymphatic vessels coming from the mouth and nose ; 

 and in morbid states of these parts, such as glanders, the glands become 

 inflamed and enlarged from the irritant matters conveyed in the lymphatic 

 vessels. They should be carefully excised to expose the submaxillary 

 artery and the inferior belly of the digastricus muscle. 



The Submaxillary or Facial Artery (Plate 27) appears at the 

 upper part of the space, descending between the subscapulo-hyoid and 

 internal pterygoid muscles. At this point the inferior extremity of 



