508 'Journal of Comparative Neurology and Psychology. 



side a small aneurism is situated at the origin of the posterior communicating artery from the carotid, 

 and one at the junction of the right anterior cerebral and anterior communicating artery. (Fig. 6.) 



Case 2169. A. J. L.; white; male; aged 72; epileptic dementia. Arterio-sclerosis. Right anterior 

 cerebral artery large, left small; and distributed mainly to the lower medial surface. A large median 

 cerebral artery takes the place of the left anterior cerebral, and after it passes the genu it is distributed 

 to the left upper medial surface and forms a callosal branch. Both posterior communicating arteries 

 are enlarged; left posterior cerebral artery quite small. (Fig. 6.) 



Case 2172. F. J. L.; white; male; aged 64; senile dementia. Arterio-sclerosis. Right anterior 

 cerebral artery sends a large callosal branch which afterwards divides and supplies both quadrate 

 lobules, while another branch of this artery forms the callosal branch of the left side. Right vertebral 

 artery small; left continuous with the basilar and of the same size. 



Case 2176. P. C; white; male; aged 66; senile dementia. Marked arterio-sclerosis. Posterior 

 communicating artery of left side large; posterior cerebral small, mainly distributed to velum inter- 

 positum, crus, and a small branch which joins the posterior communicating artery about one-half inch 

 from its origin. The posterior communicating artery of this side, therefore, chiefly furnishes the 

 posterior cerebral region. 



Case 2177. D. P.; colored; male; aged 63; senile dementia. Arterio-sclerosis. Right posterior 

 cerebral artery very small, and joins the posterior communicating artery by a small impervious branch. 

 This artery is distributed mainly to the crus, and a large artery corresponding with the anterior choroid 

 runs backward in the fissura hippocampi and after supplying the choroid plexus takes the place of the 

 posterior cerebral artery being distributed in the same way. A small branch from this anomalous vessel 

 anastomoses with the posterior choroid artery. The right posterior inferior cerebellar artery arises from 

 the basilar; the opposite artery arises by a common trunk with the anterior inferior cerebellar. Fig. 6. 



Case 2179. J. F.; white; male; aged 69; senile dementia. Advanced arterio-sclerosis. Both 

 posterior communicating arteries are large and furnish the region of the posterior cerebral arteries. The 

 left posterior communicating artery communicates with the basilar artery by a small impervious branch; 

 the right anastomoses with the superior cerebellar by a small pervious branch; both posterior cerebral 

 arteries being practically absent. The left anterior inferior cerebellar artery is very small. 



Case 2184. W. T.; white; male; aged 57; chronic epileptic dementia. No arterial disease. Both 

 posterior communicating arteries are small and are distributed mainly to parts around the crura. The 

 left anastomoses with the posterior cerebral artery by a small branch, the right has no connection with 

 the posterior cerebral artery. The nutrient arteries of the interpeduncular space are larger than usual, 

 otherwise the posterior cerebrals are normal. 



Case 2189. M. J.; colored; female; aged 65; senile dementia. Arterio-sclerosis. Both posterior 

 communicating arteries small; both posterior inferior cerebellar arteries arise in common with the 

 anterior from the basilar. Small impervious trunk connects the two anterior cerebral arteries posterior 

 to the anterior communicating. 



