28 Sketch of & General Theory of the ! (Jory, 
he was'right in assigning to'the cerebellum the involuntary motions ; 
but erred in excluding the voluntary ones; for the cerebellum is the 
source of all motion, voluntary and involuntary, as I'shall show in’ 
the sequel : while it is: the source of every impulse on the muscular 
system, voluntarity is changed into involuntarity only by ganglia on 
the cerebellic nerves. I must, however, remark, that even if 
Willis had stated that which is accurately true, and grounded his’ 
statements, as he has done, only on conjecture, or on proofs which 
do not deserve the name, I should not have thought of yielding to 
him the merit of! observing this truth ; for even then’ he would 
equally have proved that “ the dura mater administers heat for the 
distillation of the spirits,” ‘* that the pia mater does by’ chemical 
artifice insti] the animal spirits into the brain'and cerebel,” and in- 
numerable other absurdities—all of which, as well as this one, he 
supports by ridiculous conjecture, and not by argument, Even 
truth, however, if struck out only by wild conjecture, and unsup- 
ported by proof, would not constitute discovery : the mental effort’ 
of rational conjecture, and the personal one of “ careful examina- 
tion” would still remain to be performed by some one who, if 
successful, would certainly deserve the honour as well as the labour. 
And now, Sir, 1 can furnish Dr. Leach with a quotation from the 
great work of Baron Haller—a more recent and a better writer 
than Willis, which will be just as much to his purpose as his own 
“ accurate” reference to Willis ; but which I nevertheless deem ‘it 
necessary to state, in order that the history of this important ques- 
tion may be completely before the reader. “ Convulsiones artuum,” 
says he,  constanter vidimus in animalibus supervenisse, quorum 
cerebellum vulneraveramus.—Et de convulsionibus dictum est, que 
sunt musculorum voluntariorum. Ex cerebello etiam, si ullus, 
quintus sensu? destinatus et voluntario mou: nervus prodit. Quare 
collectis omnibus, videtur cerebellum et a cerebro hactenus parum 
differre, et graves in utrovis lasiones mortem inferre, leviores in 
utroque tolerari. Deinde cerebrum ad vitalia organa et sentientem 
vim et moventem mittere, et ad partes mentis arbitrio subjectas cere- 
bellum.” Here, then, it appears that Haller, after proceeding 
upon an ‘‘ it is said” as to the convulsion of the voluntary muscles; 
observing that the fifth pair coming from the cerebellum is, how- 
ever, destined both to sense and motion; and thinking that, upon 
the whole, the cerebellum in so far differs little from the cerebrum, 
—~at last concludes that the cerebrum seems to send both feeling 
and moving power to the vital organs; while the cerebellum sends 
both feeling and moving power to the parts which are subject to the 
will. Now, from this, I differ by asserting, that the cerebrum sends 
neither sensation nor motion to any part, but merely receives sen- 
sation from the organs of sense; while the cerebellum has not only 
nothing to do with sensation, as Haller erroneously asserts, but 
sends motion both to the voluntary and to the involuntary parts— 
or, in other words, both to the mechanical or locomotive, and te 
