( *5 > 
Sleepinefs in that Manner, but in a different 
Way, which fhall bedefcribed in the Sequel of this 
Difcourfe. 
Thus this Pofition concerning what has been gene- 
rally eileemed a mechanical Caufe of Sleep after 
Meals, being, I think, fufficiently refuted, it remains 
that I endeavour to eflablifh fuch a general Caufe of 
Sleep, as may be conformable to what is advanced in 
the Eifay under Confederation. 
I believe it will hardly be denied, that the Caufe 
of Sleep in general is a Want of a fufficient Quan- 
tity of animal Spirits for. the Ufe and Exercife of the 
animal Funftions: Therefore whatever prevents their 
Recruit ; hinders or impedes their Secretion ; abforbs 
or fetters them when produced j and whatever ex- 
haufls or evaporates them, by occafioning a Paucity 
of Spirits, will, in a healthy Perfon, produce a Lift- 
lefl'nefs, Lazinefs, a Tendency to Sleep, or Sleep it- 
felf, in Proportion to that Paucity of the remaining 
Spirits. 
If we enumerate all the known remote Caufes of 
Sleep or Sleepinefs, we fhall find that in fome one or 
other of the Ways above fet down, they do all of 
them tend to produce this immediate or proximate 
Caufe, to wit, an Impairment of the nervous Fluid, 
or animal Spirits, and thereby bring on thefe feveral 
Difpofitions to Sleep, or Sleep itfelf. 
All the remote Caufes of Sleep, or Sleepinefs, 
I think may be fully comprehended in the four 
following Particulars, and conlidered in the follow- 
ing Order. 
I. Exer» 
