1 BEAN. 



of the anatomy of the central nervous system, and the more objective the 

 presentation, the better will it be understood. The present first, second, 

 and third year classes in the Philippine Medical School composed of 

 Filipinos from all parts of the Archipelago have utilized successfully a 

 scheme of study that is presented in brief below. The first portion of 

 this scheme was employed by me when teaching "brain dissection" at 

 the University of Michigan (1905-1907), and I am indebted to Professor 

 J. Playfair McMurrick for the essential outline, but the details have 

 been somewhat altered. The study of the central nervous system follows 

 the dissection of the human body, and is the conclusion of the course in 

 histology and embryology. 



First dissect the spinal cord and study the gross details, then examine 

 the brain box with the dura mater, sinuses, and emerging nerves, after 

 which survey the brain as follows : 



The dura mater is left in the skull because of its intimate adherence to the 

 base: 



The arachnoid, a fibery web between the dura and pia mater, is adherent to 

 the pia mater for tlie most part, but separated from it by a distinct space, the 

 subarachnoid space. 



The pia mater is on the surface of the brain. 



Behind the cerebellum is the cerebellomeduUary subarachnoid cistern. 



At the base of the brain occupying the interval between (a) the pons, (6) 

 the temporal poles, and (c) the optic commissure is the interpeduncular subarach- 

 noid cistern pointed like a five-rayed star by prolongation into (a) the tentorial 

 fissures between the cerebrum and the cerebellum, (/3) the lateral fissures 

 (Sylvius) anterior to the temporal lobes, and (7) the longitudinal fissure anterior 

 to the optic commissure. The subarachnoid space is continuous with the same 

 space around the spinal cord and also with the brain ventricles and the central 

 canal of the cord through (a') the median aperture of the fourth ventricle 

 (Magendie), and {V) the two lateral recesses for the choroid plexuses at the 

 base of the temporal lobes. 



Xote the arrangement of the blood vessels: veins mainly in the roof; arteries 

 at the base. The direction of blood flow is upward in each, with downward 

 return through the sinuses. 



Arteries: Three sets, namely («) on the brain surface, anterior, middle, and 

 posterior cerebral; (6) median ganglionic branches into the base of the brain and 

 basal ganglia; (c) choroid arteries to the brain cavities. 



The circle of Willis is formed by: 



I. The basilar artery, produced by the union of the vertebrals from the subclavian. 



Ventral to the pons it divides into two equal branches : 

 1. Posterior cerebral arteries from which are given off: Superior cerebellar 

 arteries. The third nerve between (a) and (b) should be noted. 



II. The internal carotid arteries which give off: 



1. Posterior communicating arteries to join the posterior cerebral. 



2. Middle cerebral arteries which enter the lateral fissvires (Sylvius). 



3. Anterior cerebral arteries, the ventral continuation of the internal carotid 



arteries, and 



4. Anterior communicating connecting the two (c). 



