LOOKING-GLASS. 
101 
than in other animals, their point, formed by the 
narrow part that joins the bones, does not exceed 
an angle of forty-fiv^e degrees. Thus the whole 
body receives a fufficient prop ; for, were not the 
upper (lory fecured, the ftru£ture would give way, 
from its pretTure and natural bias ; only one mufcle, 
however, promotes the forward motion, while fo 
many othefs keep it up. 
In fliort, the head is kept fteady by the fpine of 
the neck, extended by various fibres, whofe elaftic 
force keeps it from reeling in deep ; while its gentle, 
forward motion, is favoured by a few inconfiderable 
firings. The crane, as we may call it, is likewife 
ballafted, or fortified, in fuch a way as prevents it 
from leaning improperly to either fide. 
All thefe, and other parts, move continually 
while we ftand ; fo that eafe is naturally fought 
by a change of attitude, and alternately moving on, 
or fhifting the foot that bears the burden. 
H 3 
ESSAY 
