THE ARACHNOID OF THE BRAIN.(') 



F. W. Langdon, M.D., 



Professor of Surgical Anatomy in Miami Medical College, Cincinnati. 



I. Its General Homology with the Serous Membranes of the 

 Other Great Cavities. 



Modern works on human anatomy do not give, as a rule, 

 an account of the cerebro-spinal arachnoid, which is, in the 

 opinion of the writer, in harmony with its structure, topog- 

 raphy, and relations as shown by dissection. 



Some of the different views which have existed respecting 

 the subject, as well as the present consensus of opinion of 

 our commonly accepted authorities, are exhibited in the 

 following historical notes: 



According to Bichat,(^) " in the middle of the seven- 

 teenth century it began to be suspected that . . . the 

 arachnoid and pia . . . might possess a separate exist- 

 ence." "The Anatomical Society of Amsterdam assured 

 themselves of the fact in 1665; Van Home soon after demon- 

 strated the arachnoides separately to his pupils." 



Bichat himself (') describes the arachnoid as a serous shut 

 sac, conforming in all essential particulars with the serous 

 membranes of the other cavities. This was apparently the 



1 Read before the Association of American Anatomists at the annual meeting, Boston, 

 December 59, i8go, and reprinted from the N. Y. Medical Record, August 15, 1891. 



2 Xavier Bichat, etc., " A Treatise on the Membranes in General, and on Different 

 Membranes in Particular," Paris, 1802. Translated by John G. Coffin, M.D. Boston, 

 1813, p. 163. 



3 Op. cit. 



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