CEPHALCKRACHIDIAN FLUID. 263 



araclmoid space, but it is the most definite estimate that has 

 been given. 



The discharge of a certain quantity of the cephalo-rachid- 

 ian fluid does not produce any marked derangement in the 

 action of the nervous system. In the first experiments of 

 Magendie, in which the muscles of the neck and the occipito- 

 atloid ligament were divided, the animals were affected with 

 irregular movements, general paralysis, etc. ; * but it is stated 

 by Longet 2 and by Bernard, that these phenomena are due 

 to the division of the parts involved in the operation, and 

 not to the removal of the liquid. When the liquid is al- 

 lowed to flow spontaneously through a small trocar intro- 

 duced without division of the muscles of the neck, there fol- 

 lows no serious nervous disturbance ; but when the liquid is 

 drawn out forcibly with a syringe, the animal first becomes 

 enfeebled, and afterward seems affected with general paraly- 

 sis. These phenomena are attributed by Bernard, not so 

 much to removal of the fluid, as to congestion of blood-ves- 

 sels and even effusion of blood, which follow sudden dimi- 

 nution in the pressure. 3 



Sudden increase in the quantity of liquid surrounding 

 the cerebro-spinal axis produces coma, probably from com- 

 pression of the centres. This was shown by Magendie, by 

 injecting water in animals, and also by compressing the tu- 

 mor, in cases of spina bifida in the human subject, by which 

 the fluid was pressed back into the spinal canal. In the 

 cases of spina bifida, the subject, during the compression, 

 fell into coma, which was instantly relieved by removing 

 the pressure. 4 



It was ascertained by Magendie, and this has been con- 

 firmed by all later observers, that the cephalo-rachidian fluid 



1 MAGENDIE, Liquide cephalo-rachidien, Paris, 1842, p. 58. 



2 LONGET, Traite de physiologic, Paris, 1869, tome iii., p. 305. 



3 BERNARD, Sy&teme nerveux, Paris, 1858, tome i., p. 496, et seq. 



Bernard states that Magendie recognized the error in his first interpretation of 

 the phenomena following removal of the cephalo-mchidian fluid (Ibid., p. 496). 



4 MAGENDIE, op. cit., p. 60. 



