TRANSACTIONS OF THE SECTIONS. 449 



haps, concluded from this circumstance that this species of in- 

 sect will ultimately become naturalized in this climate. 



Abstract of Observations on the Structure and Functions of the 

 Nervous System. By James Macartney, M.D., Professor 

 of Anatomy and Surgery in the University of Dublin. 



The author begins by stating the received opinion respecting 

 the structure of the brain, as consisting of two substances ; the 

 one an opake white pulp, which is considered to be the nervous 

 matter ; the other a coloured substance, in some places inclosing 

 the white, and at other places being imbedded in it. 



It has been long known, he adds, that the white substance in 

 many parts assumes the shape of bands or bundles of fibres. 

 Dr. Spurzheim did not hesitate to call these fibres nerves, and 

 was more successful in tracing their course in some parts of the 

 brain than his predecessors had been. 



But the author has employed a method of dissecting the brain, 

 which has enabled him to discover that all our former ideas with 

 respect to the structure of the cerebral organ fall far short of 

 the intricacy with which its several parts are combined. 



In order to perceive the real structure of the brain, recent 

 specimens are necessary. The sight should be aided by spec- 

 tacles of a very high magnifying power ; and as the different 

 parts are exposed in the dissection, they should be wetted with 

 a solution of alum in water, or some other coagulating fluid. By 

 these means it will be observed that all the white substance, 

 whether appearing in the form of bands, cords, or filaments, or 

 simply pulp, are composed of still finer fibres, which have a 

 plexiform arrangement, and that all those fibres, to the finest 

 that can be seen, are sustained and clothed by a most delicate 

 membrane. By the same mode of dissection, also, it is possible 

 to make apparent the existence of still finer interwoven white 

 fibres in all the coloured substances of the brain, in many of 

 which the nervous filaments are so delicate and transparent that 

 they are not visible until in some degree coagulated by the so- 

 lution of alum or by spirits. 



Dr. Macartney has thus been enabled to see twenty-six 

 plexuses not hitherto described in the brain, the fibres com- 

 posing which assume two arrangements, the one reticular, the 

 other arborescent. 



The membrane mentioned as pervading the entire substance 

 of the brain, and supporting its delicate organization in every 

 part, has hei'etofore escaped the observation of anatomists, and 

 yet when the fact is declared, we at once perceive that such a 



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