2o8 



Journal of CoMPAUAmE Neurology. 



The writer regrets that material and time have not per- 

 mitted these observations to be carried to thei»- logical con- 

 clusion, by actual sections of cranial nerve exits, to show^ the 

 arachnoid reflections. 



Diagram A. \'ertical Transverse Section of Parietal Region to 

 Show the Various Membranes and their Layers. — i, Sutural "liga- 

 ment," continuous with external periosteum and periosteal layer of dura; 

 2, parietal bone; 3, periosteal layer of dura; 4, inner layer of dura, form- 

 ing sinuses; 5, subserous connective tissue, between dura and parietal 

 arachnoid; 6, parietal arachnoid; 7, arachnoid cavity; 8, visceral arach- 

 noid; 9, subarachnoid space; 10, pia mater; S, superior longitudinal 

 sinus; s, inferior longitudinal sinus; F, falx; C, convolutions. 



2. The Coni7iiunications bctzveen the Arachnoid Cavity and 



the Subarachnoid Space by Way of the " Lunulate 



Foramina^ 



During the progress of the last dissection it was evident 



that there were two points at the base of the cranium where 



the arachnoid was deficient over a considerable area on either 



side of the medulla oblongata. These deficiencies present 



the form of bilateral foramina — one on each side — and are 



situated in the " bridge" of visceral arachnoid which stretches 



across from the cerebellar lobes to the under surface of the 



medulla. These foramina measure about half an inch in 



longitudinal diameter by one-fourth inch transversely, and 



are crossed by three or four fibrous bands, the attachment of 



