The Hal Gs 1) OR fey 
the fibres, of which the mufcles are compofed, 
and confequently. by the fubfiding of the adja- 
cent parts, rather than by any inflation of thofe 
parts of which they themfelves confift; as the 
authors, who have hitherto treated this fubject, 
have falfly imagined. Seventhly, and laftly, 
therefore, I from hence conclude, that all the 
actions of the mufcles confift in contraction, 
or in a return to that form and difpofition they 
had before they were dilated ; fo that the muf- 
cles, as often as they are again dilated, or de- 
termined a contrary way, by the caufe already 
affiened, or by means of their conterts, or by 
the action of the antagonift mufcles, conftantly 
return afterwards to their former ftate of con- 
traction, whether the motions they are to give 
be natural or voluntary. 
Though this be ufually the cafe, and prin- 
cipally with regard to the natural motions of 
the mufcles, it neverthelefs is obferved to take 
place in their voluntary motions alfo; though, 
to effeét thefe laft, the confent of the will is 
likewife neceflary. For we find, that, in all 
the voluntary motions of the mufcles, there is 
likewife abfolutely required fome internal or 
external caufe, by means of which a contrac- 
tion of the antagonift mufcles may be deter- 
mined another way. 
Therefore, fince all the mufcles are in a 
perpetual ftate of contraction, it is eafy to con- 
ceive, that the leaft degree of determination, 
whatever caufe may ferve to produce it, is fuffi- 
cient to difpofe them to move the body, make 
it advance, remove it from place to place, and 
actuate it in a thoufand other different ways. 
Nor is it in natural motions alone, that 
things are obferved to proceed in this manner, 
as plainly appears by the contraction of the 
pupil of the eye, which inftantaneoufly ex- 
pands and dilates itfelf, by means of its muf- 
cles, as the eye is more or lefs irritated by the 
particles of light. The fame may be obferved 
of the moving fibres of the inteftines, which 
conftantly alfo contract and expand themfelves, 
in proportion to their contents; fo that their 
motion perfectly refembles that of the fea, 
whofe waves follow and mutually prefs upon 
one another. 
We often obferve, that a natural contraction 
takes place in thofe mufcles, which are faid to 
move as the will directs; as is manifeft in our 
walking, ftanding, and making ufe of our 
hands: for we certainly move our limbs almoft 
every moment, without reflecting in the leaft 
upon what we do. ‘Thus, with regard to ex- 
ternal objects, we often falute a perfon we 
meet, merely becaufe another in our company 
takes off his hat, or becaufe we are affected by 
fuch external obje@, though we do not know 
who the perfon is we have faluted, nor fo much 
as think of our faluting him. For this reafon 
therefore it is plain, that as our memory is 
local, and is affifted by the image of one thing 
in pafling to that of another, and fo on without 
end, the contractions of our mufcles are in like 
manner natural; and the mufcles themfelves 
are urged by one caufe of motion to another, 
oie 1 SOUR) Oy: 
131 
and from this to a third, and fo on without any 
interruption, 
It is for a fimilar reafon, that, when we find 
ourfelves too near the fire, we retire to a greater 
diftance-from it, and put our limbs, by means 
of various motions, into their former pofture, 
without attending in the leaft to what we do; 
but merely in confequence of the impreffion 
made upon us by the irritating obje. From 
hence it appears, that we can never be truely 
faid to move voluntarily, unlefs when the will 
itfelf is put in motion by the object, and then 
by its own motion produces a third; for when- 
ever the light happens to be too ftrong, we {hut 
our eyes, turn our head afide, and give our- 
felves many other motions, as we are varioully 
excited to them by the objects that prefent 
themfelves. 
All thefe facts abundantly prove, that thofe 
very mufcles, by whofe affiftance we perform 
our voluntary motions, are notwithftanding 
always themfelves moved in a natural manner, 
not only becaufe an internal or external prin- 
ciple, caufe, or obje@ is alone requifite to de- 
termine them; but likewife becaufe a volun- 
tary motion is never produced, unlefs fuch a 
determining principle, whatever that may. be, 
precedes it, though it fhould be but a thought 
merely cafual, let alone one previoufly. excited. 
Cannot a fimple dream, or fome abfolute phan- 
tom, prefenting itfelf before us in the night, 
fo affect us? Even in this cafe, we immediately 
ftart, tremble, and perhaps get out of bed, 
fhrick, and call for affiftance. And all this 
we do merely becaufe we then juft determine 
another way our mufcles, already prepared for 
action. We may obferve the fame things alfo 
in our {pontaneous or natural motions, though 
fuch motions can be but very feldom deter- 
mined by us, and that alfo under certain con- 
ditions only. For our will, as I took notice in 
the beginning, has very little power in deter- 
mining fuch of the mufcles as have no anta- 
gonifts; and indeed, if nature had not be- 
ftowed upon us fuch antagonift mufcles, we 
fhould have been little better than vegetables, 
which cannot ftir from the place wherein they 
have taken root. 
It is evident, from the foregoing obfervations, 
that a great number of things concur in the 
contraction of the mufcles; and that we thould 
be thoroughly: acquainted with that wonderful 
machine our body, and the elements with 
which we are’ furrounded, to defcribe exactly 
one fingle mufcle, and explain its aGtion, ina 
fatisfactory manner. On this occafion, it would 
be neceflary for us to confider the atmofphere, 
the nature of our food, the blood, the brain, 
marrow, and nerves, that moft fubtile matter 
which inftantancoufly flows to the moving 
fibres, and many other things, before we could 
expect to attain a fight of the perfect and cer- 
tain truth. For my part, I own that I have 
endeavoured to offer fomething on this impor- 
tant fubject worth the publick’s acceptance ; 
but yet Iam fenfible, that all this time I have 
been, as it were, reprefenting with a coal the 
fun’s 
