970 THE VASCULAK SYSTEM, 



The occipital diploic vein is usually the largest of the series ; it drains the 

 occipital bone, and terminates either externally in the occipital vein or internally 

 in the lateral sinus. 



Venae Meningeae. The meningeal veins commence in two capillary plexuses, 

 a deep and a superficial. The deep plexus is a wide-meshed network in the inner 

 layer of the dura mater. Its efferent vessels terminate in the superficial plexus. 

 The superficial plexus lies in the outer layer of the dura mater. It consists of 

 numerous vessels of uniform calibre which frequently anastomose together, and 

 terminate in two sets of efferents ; of these, one set ends in the cranial blood sinuses, 

 and the other accompanies the meningeal arteries. The efferent meningeal veins 

 are peculiar, inasmuch as they do not alter much in size as they approach their 

 terminations. They lie external to the arteries in the grooves in the inner wall 

 of the cranium, and are very liable to be torn when the bones are fractured 

 (Wood Jones). 



VEINS OF THE BRAIN. 



The veins of the brain include the veins of the cerebrum, of the mid-brain, of 

 the cerebellum, of the pons, and of the medulla oblongata. They do not possess 

 valves. 



Venae Cerebri The Veins of the Cerebrum. The cerebral veins are arranged 

 in two groups, (a) the deep and (&) the superficial. 



The deep veins issue from the substance of the brain. The superficial veins lie 

 upon its surface in the pia mater and the subarachnoid space. The terminal 

 trunks of both sets pierce the arachnoid membrane and the inner layer of the dura 

 mater, and open into the cranial venous sinuses. 



(a) The deep cerebral veins are the chorioid veins, the venee terminales, 

 the internal cerebral veins, the great cerebral vein (Galen), the vein of the septum 

 pellucidum and the inferior striate veins. 



Each chorioid vein is formed by the union of tributaries which issue from the 

 chorioid plexus in the body and inferior horn of a lateral ventricle. It ascends, 

 along the lateral border of the tela chorioidea of the third ventricle (O.T. 

 velum interpositum), and passes forwards, in the lateral border of that fold of pia 

 mater, to the interventricular foramen (Monro), where it receives efferents from 

 the chorioid plexus of the third ventricle, and unites with the vena terminalis to 

 form the internal cerebral vein (Galen). 



The vena terminalis (O.T. vein of corpus striatum), on ieach side, is formed by 

 the union of tributaries which issue from the corpus striatum and from the 

 thalamus. It runs forwards between the thalamus and the caudate nucleus, in a 

 groove in the floor of the lateral ventricle, and, after receiving tributaries from the 

 walls of the anterior horn of the ventricle, and the vein of the septum pellucidum, 

 it terminates at .the apex of the tela chorioidea, where it joins the chorioid vein to 

 form the internal cerebral vein (Galen). 



Each internal cerebral vein (Galen) commences at the apex of the tela 

 chorioidea, near the interventricular foramen (Monro), by the union of the 

 vena terminalis with the chorioid vein. The two veins run backwards between the 

 layers of the tela, receiving tributaries from the chorioid plexuses of the third 

 ventricle and from the fornix and corpus callosum, and they terminate, beneath 

 the splenium of the corpus callosum, by uniting to form the great cerebral vein 

 (Galen). 



The great cerebral vein (Galen) passes backwards and slightly upwards from its 

 origin, and ends in the anterior extremity of the straight sinus. In addition to 

 the two internal cerebral veins, by the union of which it is formed, it receives 

 tributaries from the posterior parts of the gyrus cinguli of each side, from the pineal 

 and quadrigeminate bodies, from the medial and inferior surfaces of the occipital 

 lobes of the brain, and from the upper surface of the cerebellum. It also receives 

 the basal vein of each side (see p. 971). 



An inferior striate vein descends, on each side, from the substance of the corpus 

 striatum, and, after passing through the anterior perforated substance, ends in the 



