THE ROOF AND LATERAL RECESSES OF THE 

 FOURTH VENTRICLE, CONSIDERED MORPHO- 

 LOGICALLY AND EMBRYOLOGICALLY. 



By Joseph A. Blake, M.D. 



[Read before the Association of American Anatomists, Eleventh Annual Ses- 

 sion, New York, Dec. 28, 1898.] 



My investigations on this subject were prompted by the 

 contradictory opinions and the lack of absolute knowledge con- 

 cerning the nature of the communications between the cavity 

 of the fourth ventricle and the subarachnoid space. 



At first my efforts were confined to the study of the mor- 

 phology of the metapore, or foramen of Magendie, but I soon 

 found that it was necessary to include that of the entire roof of 

 the ventricle, and then naturally followed an elucidation of the 

 problems found in the lateral recesses. 



The development of the roof of the ventricle is very 

 closely connected, it is needless to say, with that of the oblon- 

 gata and cerebellum. 



The development of the oblongata in man has been worked 

 out by His, but we need further knowledge of its development 

 in the lower animals. Our knowledge concerning the cerebel- 

 lum is as yet unsatisfactory. 



The lateral recesses have been ably described by Mihalco- 

 vics and by Retzius, but the descriptions in our text-books are, 

 as a rule, faulty, if not incorrect. 



Their relations to the medulla and cerebellum and their 

 segmental value have not been sufficiently determined. 



Hitherto the investigations on the metapore and foramina 

 of Luschka have been chiefly to determine their presence, 

 while their nature has been largely a matter of supposition. 

 The methods employed have been almost entirely those of in- 



