78 THE DISEASES AND DISORDERS OF THE OX. 



bifurcation of the transverse facial, a branch of the superficial 

 temporal artery. The internal maxillary artery has no pterygoid 

 foramen to pass through in any domesticated ruminant. The 

 largest of the arterial plexuses or retia mirabilia inside the cranium 

 are formed by branches from the internal maxillary artery. One 

 of these branches, the spheno-spinal, enters the cranium by the 

 foramen ovale, and, as a rule, two arteries to the rete enter by the 

 anterior common foramen. The first of these inclines forwards, 

 the two latter backwards. The three arteries anastomose by 

 forming a small and intricate plexus known as the cranial rete 

 mirabile. It is situated at the side of the sella turcica of the 

 sphenoid bone, communicating with its fellow posteriorly, and 

 giving off superiorly the encephalic artery ^ a branch considered 

 by Chauveau to be analogous to the intracranial portion of the 

 internal carotid in the solipede. 



From this artery are given ofi" the cerebral arteries — anterior, 

 middle, and posterior. The last passes backwards, and forms a 

 convergent anastomosis with its fellow, thus constituting the 

 basilar trunk which leads to the middle spinal artery. Another 

 arterial plexus is formed on the ophthalmic artery just where the 

 arteries of the eye are given ofi". The glosso-facial artery is 

 present only in the larger ruminants. 



Veins. — The subcutaneous abdominal vein is very large in 

 the oxj the subcutaneous thoracic vein being small in proportion. 

 The saphenous veins differ from those of the horse, the external 

 saphenous vein being larger than the internal one. 



The valves in the veins are well developed. Each vena 

 azygos of the two so-called may persist. In some antelopes the 

 left vejia azygos is larger than the right azygos vein. In 

 ruminants the portal veins have valves, and in these animals 

 there is provision made for the blood making its way by two 

 openings, one at the base of the temporal, the other, as in the 

 case of human beings, through the foramen lacerum posterius. 

 There is one anterior vena cava. 



The jugular vein is large, and there is a small accessory jugu- 

 lar vein which varies much in size, originating in the occipital 

 vein and joining the great jugular vein near its termination. The 

 angular vein of the eye is very prominent in small ruminants. 

 There are three digital veins of the hind limb, including an ante- 

 rior or common one between the digits, formed by twigs from the 



