VEINS OF THE DIPLOE. 



465 



named according to the arterial branches which they accompany, join to form 

 a short single trunk, which leaves the orbit by the inner part of the 

 sphenoidal fissure, where it is placed between the heads of the external 

 rectus muscle, and terminates in the cavernous sinus. 



Not unfrequently one of the frontal veins is much larger than the others, and, 

 descending vertically near the middle of the forehead, joins the facial and a branch 

 of the ophthalmic vein on one side of the root of the nose. 



VEINS OF THE DIPLOE. 



The veins of the dip!oe of the cranial bones are only to be seen after the 

 pericranium is detached, and the external table of the skull carefully re- 

 moved by means of a file. Lodged in canals hollowed in the substance of 

 the bones, their branches form an irregular network, from which a few 

 larger vessels issue. These are directed downwards at different parts of the 

 cranium, and terminate, partly in the veins on the outer surface of the 

 bones, and partly in the sinuses at the base of the skull. 



Fig. 316. 



Fig. 316. VEINS OF 



THE DlPLOE OF THE 



CRANIAL BONES (after 

 Breschet). 



The external table 

 has been removed from 

 the greater part of the 

 calvarium so as to ex- 

 pose the diploe and the 

 veins which have been 

 injected. 1, a single 

 frontal vein; 2, 3, the 

 anterior temporal vein 

 of the right side ; 4, 

 the posterior temporal ; 

 5, the occipital vein of 

 the diploe. 



According to Bres- 

 chet there are four 

 such veins on each 

 half of the cranium, 

 viz., a frontal, occipital, and two temporal. 



The frontal is small, and issues by an aperture at the supraorbital notch to join 

 the vein in that situation. There is often only one frontal vein present. 



The temporal are distinguished as anterior and posterior. The anterior is con- 

 tained chiefly in the frontal bone, but may extend also into the parietal, and opens 

 into the temporal vein, after escaping by an aperture in the great wing of the sphe- 

 noid. The posterior ramifies in the parietal bone, and passes through an aperture at 

 the lower and hinder angle of that bone to the lateral sinus. 



The occipital is the largest of all ; and leaves the occipital bone opposite the infe- 

 rior curved line to open, either internally or externally, into the occipital sinus or 

 the occipital vein. Its ramifications are confined especially to the occipital bone. 



VEINS OF THE UPPER LIMB. 



The veins of the upper limb are divisible into two sets, the superficial, 

 and the deep-seated. Both sets are provided with valves, and these are 



