THE MENINGES AND BLOOD SUPPLY G25 



oue of which is distributed through the pia mater to the adjacent white 

 matter of the spinal cord and to the gray pallium of the brain; the other 

 penetrates the spinal cord through the anterior median fissure by a 

 series of small fissured arteries to be distributed to the central gray mat- 

 ter, and in the brain is represented by the branches of the middle cere- 

 bral arteries which penetrate directly to the ganglionic gray matter in 

 the interior of the cerebrum. 



In the spinal cord the vessels of the former set are mostly distributed 

 to the white cortex, the larger branches, however, penetrate the white 

 matter and aid in the formation of the capillary network of the gray 

 medulla. In the brain their distribution is similar, the smaller pial 

 vessels, the cortical arteries,, being distributed to the cortex, which in this 

 case is formed by the gray matter; the larger, the medullary arteries, 

 penetrating to the white medulla in which they break up into capillary 

 vessels. 



The veins trend in the opposite direction and in the pia mater col- 

 lect into large vessels, which in the brain open into the sinuses of the 

 dura mater, and which in the spinal cord form the ventral and dorsal 

 median veins. 



All of the larger vessels receive thin fibrous investments from the 

 pia mater; the smaller vessels and capillaries are surrounded by neu- 

 roglia. 



There are frequent anastomoses between the larger veins ; the arteries, 

 however, are all terminal arteries according to Cohuheim's classification, 

 possessing no anastomoses with the capillary areas of other vessels. 



Neither brain nor cord possess true lymphatics. The sole lymphatic 

 representatives within the central nervous system are pericellular and 

 perivascular spaces communicating with subpial spaces and ultimately 

 through uncertain clefts and channels with the subarachnoid spaces. 



