MEDIAN ANTERIOR CEREBRAL ARTERY 187 



In a typical median anterior cerebral artery, the description 

 is as follows : 



The vessel arises from the anterior communicating artery, 

 usually near the middle; curves upward, and in close proximity 

 to the lamina terminalis, around the genu of the callosum, lying 

 close to this body; and at about the middle or at the junction 

 of the anterior two-thirds with the posterior third of the callo- 

 sum it divides into two nearly equal branches which are dis- 

 tributed to the paracentral lobules and the quadrate lobules of 

 the opposite hemispheres. In the course of the main trunk 

 and the principal branches of the vessel, small and unimportant 

 branches are given off to the lamina terminalis, the callosum, 

 and to the adjoining gyri, but these ultimate branches have not 

 been worked out, and are perhaps relatively unimportant. A 

 large majority of these aberrant vessels have this origin and 

 distribution, though occasionally the origin may be nearer to 

 one anterior cerebral artery than the other. It may even seem 

 to originate from one of these vessels near to the junction with 

 the communicans, or what is still more important for our study, 

 it not infrequently arises from the end of the junction of the 

 two anterior cerebrals when these are fused and the anterior 

 communicating artery as such is absent. 



Differences in the size and distribution of the main branches 

 are occasionally met with; sometimes one branch may be want- 

 ing, and the vessel is then distributed to one side only. In the 

 small or undeveloped vessels as those described by Wilder, the 

 branches are all small and irregular, and are sent mainly to the 

 lamina terminalis, the rostrum callosi, and the gyri in the immedi- 

 ate vicinity. 5 



In an article by Grunbaum and Sherrington in Brain, 1902, 



'I find that on carefully removing the basal arteries and floating them out in 

 water, often a long, slender, arteria termatica is unexpectedly revealed. This 

 leads me to suspect that arteries of this type are quite frequently present but are 

 undiscovered; probably the percentage of median anterior cerebral arteries might 

 be nearly doubled if careful search were thus made. Whether these arteries are 

 vestigial or reversionary, it is certain that in the majority of instances no such 

 vessel arises from the anterior communicating artery, and that no corresponding 

 vessel is mentioned among the branches of the artery by most anatomists. 



