198 THE BRAIN. 



and its upper surface receives fine twigs from the lateral choroidal branch of the 

 posterior cerebral. 



The choroid plexuses of the lateral ventricles are supplied (1) by the anterior 

 choroid branch of the internal carotid which passes obliquely backwards and out- 

 wards, and enters the choroid plexus at the anterior end of the descending cornu, 

 supplying two-thirds of the plexus of the lateral ventricle ; (2) by the postero- 

 laterat choroid artery, a branch of the posterior cerebral, which supplies the 

 remaining third of the plexus. The choroid plexus of the third ventricle is 

 supplied by a branch (postero- mesial) of the posterior cerebral. The velum 



Fig. 139. FRONTAL SECTION OF THE BBAIN, SHOWING THE MODE OF ORIGIN AND DISTRIBUTION OF 



THE LENTICULO-STRIATE AND LENTICULO-THALAMIC ARTERIES. (E. A. S..) Diagrammatic. 



c.c., corpus callosum ; fo., fornix ; a.c. , anterior commissure ; a, corpus albicans ; i, infundibulum ; 

 ch., chiasma ; tr., optic tract; v.L, lateral ventricle; n.c., nucleus caudatus ; n.L, nucleus lenticu- 

 laris ; th., thalanms ; c.i., internal capsule ; d., claustrum ; am., nucleus amygdalae ; above x, artery 

 of haemorrhage. (The plan of the section is copied from Merkel. ) 



interpositum is also supplied by the two last-named branches of the posterior 

 cerebral. The parts in the quadrilateral space at the base of the brain including 

 the chiasma, the infundibulum and the corpora mamillaria receive branches directly 

 from the circle of Willis. 



For further details on the subject, which derives importance from the relation 

 of different local pathological conditions to the vascular distribution, the reader is 

 referred to a series of articles by Duret in the Archives de Physiologic for 1873 and 

 1874, to a paper by Huebner in the Med. Centralblatt, 1872 ; and to a work 

 entitled " Die luetische Erkrankung der Hirnarterien," Leipzig, 1874, by the same 

 author. 



Lymph-paths of the brain and spinal cord. Neither the brain nor the spinal cord 

 possesses true lymphatic vessels. The lymph finds its way out of these organs by means of 

 perivascular spaces in the tunica adventitia of the blood-vessels ; these perivascular spaces 

 communicate with the subarachnoid space at the surface of the brain and cord (Key and Retzius). 



