CHORD, WITH FURTHER INVESTIGATIONS INTO ITS STRUCTURE. 
351 
substance, whilst others, entering more deeply into the lateral furrows, are found to 
continue their course, nearly at right angles with the spinal chord itself, as far as the 
grey substance, in which they are lost In examining the roots of the nerves, 
I have always relied on the assistance of the naked eye only, avoiding, for fear of 
deception, the use of a lens From careful dissection, I am convinced that it is 
only a part of the fibres belonging to the two roots which are attached to the grey 
substance, and that a considerable number of threads are lost in the fibrous part of 
the chord The exact mode of their connection, however, with this latter sub- 
stance is not known.” Only a part, therefore, of Mr. Grainger’s statements is really 
correct ; for though some of the fibres of the posterior roots may be confined in their 
course within the white columns, this is certainly not the case with regard to the 
anterior roots ; and many of the fibres of the posterior roots, which appeared to him 
to be longitudinal, were probably those which take a very oblique course towards 
the grey substance. The fibres, also, of the third pair of cerebral nerves, of which 
some have been said by Mr. Grainger to be continuous with the white columns, may 
be all traced to the vesicular substance situated below the iter a tertio ad quartum 
ventriculum. Great merit, however, is due to Mr. Grainger for having made out 
so much with so little assistance. 
The question, then, arises, — Do the fibres of the posterior roots which ascend longi- 
tudinally in the posterior fasciculi transmit impressions to the sensorium ? In answer 
to this question it may be stated, — 1st, that, even if they reach the brain, their 
number appears insufficient to convey such impressions from all parts of the body; 
and 2ndly, that the anatomical connection of the posterior columns exclusively with 
the cerebellum would, a priori, lead us to a negative conclusion, unless we regard 
this latter organ as the common centre of sensation, which we have no grounds for 
believing it to be. But the same anatomical connection of the posterior columns 
with the cerebellum clearly indicates that they establish some physiological relation 
between this organ and the spinal chord ; and if the cerebellum were proved to be, 
according to the generally received opinion, a centre of motor power only, destined 
for the control and coordination of complex muscular movements, it would follow 
that these columns were motor, and not sensitive, whether or not we admit them to 
be constituted wholly, or in part, of the longitudinal fibres of the posterior roots*. 
Upon anatomical grounds, then, it would appear, that the posterior white columns 
are not the channels of communication between the sensorium and the posterior 
spinal nerves. Experimental evidence tends to the same conclusion. Both Van 
DEEN- j- and Stilling found that irritation of these columns excited no sensation 
That the cerebellum is in some way concerned in the regulation and coordination of muscular movements 
appears to follow from experiment and pathological investigation ; but I think there are reasons for believing 
that the mode of action usually assigned to it is unsatisfactory, and at variance with many well-established facts. 
The discussion of this question, however, would be foreign to the present subject. 
t Traites et Decouvertes sur la Physiologic de la Moelle Epini^re. Leide, 1841. 
MDCCCLIII. 3 A 
