SEC.iii.] CONSENSUS OF NERVES IN THE GANGLIA. 437 



nerve j but that it is necessary that these impressions be more 

 powerfuh Hence we have an explanation, why the heart is so 

 obtuse as regards sensation, and the stomach and intestine not 

 acute, namely, because impressions made on the nerves of those 

 parts do not penetrate the ganglia of the intercostal nerve to 

 reach the brain, where the perception of sensations takes place. 

 As regards the impressions, however obtuse they may be, that do 

 reach the brain from the heart, stomach, and intestines, is it 

 not rather that they reach the brain through the branches of 

 the eighth pair distributed to those viscera, than that they pass 

 through the intercostal [great sympathetic] ganglia? The 

 conjecture is difficult. Further, the structure of the ganglia, as 

 described by eminent inquirers, is not opposed to this doctrine 

 of the functions of the ganglia, but if anything rather appears 

 to confirm it. Meckel, Haase, and Zinn maintain, that the 

 ganglia are made up of the nerves entering into them, which 

 divide into very minute filaments, so that they are variously 

 subdivided, and make a sort of net-work. Condensed cellular 

 tissue is intermingled with this net-work of nervous filaments, 

 and the whole is enveloped in a somewhat tense external mem- 

 brane; whence may arise a somewhat gentle compression of the 

 nerves entering the ganglion, which is sufficient to stifle, or 

 rather intercept the less powerful impressions propagated along 

 the nerves, and manifestly to obtund the more powerful. The 

 whole of this doctrine, as to the uses of the ganglia, can how- 

 ever be brought forward only as a conjecture not manifestly 

 improbable, but meriting the investigation of the learned, and 

 possibly containing a spark of truth, from which some acute 

 genius may be able to produce greater light for us. He who 

 shall unravel the uses of the ganglia will also give a reason 

 why the fifth pair of cerebral nerves pass through the semi- 

 lunar [Gasserian] ganglia, with the exception of a fasciculus 

 which joins the third division without touching the ganglion;* 

 and why only the posterior roots of the spinal nerves enter the 

 ganglia, whilst the anterior roots pass by without any com- 

 munication with them.^ 



Further, it may be asked, whether the external impressions 

 made on the terminations of the nerves and passed onwards to 



' See my treatise ' De Structura Nervorum,' tab. ii, figs, v, \i. 

 ' Ibidem, tab. iii, figs, i, ii. 



