THE ARTERIES OF THE UPPER EXTREMITY. 



These vessels divide and ramify in the substance of the pia mater, and give off 

 nutrient arteries which penetrate the cortex perpendicularly. These nutrient vessels 

 are divisible into two classes the long and short. The long or, as they are some- 

 times called, the medullary arteries pass through the gray matter to penetrate the 

 centrum ovale to the depth of about an inch and a half, without intercommunica- 

 ting otherwise than by very fine capillaries, and thus constitute so many independ- 



FIG. 358. Distribution of the cortical arteries. (After Charcot.) 1. Medullary arteries. 1'. Group of medullary 

 arteries in the sulcus between two adjacent convolutions. 1". Arteries situated among Gratiolet's commis- 

 sural fibres. 2, 2. Cortical arteries, a. Capillary network with fairly wide meshes, situated beneath the pia 

 mater, b. Network with more compact, polygonal meshes, situated in the cortex, c. Transitional network with 

 wider meshes, d. Capillary network in the white matter. 



ent small systems. The short vessels are confined to the cortex, where they form 

 with the long vessels a compact network in the middle zone of the gray matter, the 

 outer and inner zones being sparingly supplied with blood (Fig. 358). The vessels 

 of the cortical arterial system are not so strictly "terminal" as those of the 

 central ganglionic system, but they approach this type very closely, so that injec- 

 tion of one area from the vessel of another area, though it may be possible, is 

 frequently very difficult, and is only effected through vessels of small calibre. As 

 a result of this, obstruction of one of the main branches or its divisions may have 

 the effect of producing softening in a very limited area of the cortex. 1 



ARTERIES OF THE rPPER EXTREMITY. 



The artery which supplies the upper extremity continues as a single trunk 

 from its commencement down to the elbow, but different portions of it have 

 received different names according to the region through which it passes. That 

 part of the vessel which extends from its origin to the lower border of the first 

 rib is termed the subclavian ; beyond this point to the lower border of the axilla 

 it is termed the axillary : and from the lower margin of the axillary space to the 

 bend of the elbow it is termed brachial ; here the single trunk terminates by 

 dividing into two branches, the radial and ulnar an arrangement precisely similar 

 to what occurs in the lower limb. 



1 The student who desires further information on this subject is referred to Charcot's Localisation 

 of Cei-ebral and Spinal Disease*, p. 42 et seq., whence the facts above given have been principally 

 derived. 



