Hdemajlatics. 139 
them thus heqiiently, fuddenly contrafted, 
j and fo foon relaxed again ; which make them 
like the Horfe Leech, be ever longing after 
and thirfting for more and more, thereby to 
regain the Tenfity of their too relaxed Fibres. 
5?. Thus what we take in, either as Food 
or Phyfick will have different Effefts on our 
Solids as well as Fluids, according to their 
different Natures ; and as a healthy State con- 
fifts in a due Equilibrium between the Solids 
and Fluids, it greatly imports, that they be 
rightly adapted to the different Conftitutions, 
(o as cither to invigorate, contraft or relax 
the Fibres of the Solids 5 or to change the 
Qualities or Quantities of the Fluids as occafion^ 
(hall require. 
Experiment XIX. 
I. ^ I'^Hat I might know with what deter- 
jL minate Force I impelled Air into the 
Veffels, I prepared the following Inftrumenr, 
' 'uiz. I fixed tova common brafs cylindrical Air 
Force an Elder Stick, which was two Feet 
long, and two Inches Diameter j thro' which 
a Hole of half an Inch Diameter was made from 
end CO end ; One end of an* inverted Glafs 
Syphon 
