[ 3 T 3 ] 
power of digeftion, 'and therefore that is to be 
called the true Jiomacb. In this cafe then we 
have fome diftindtion between the two grand offi- 
ces of maftication and digeftion. 
The two flat lateral fides of the grinding cavity 
are lined with a thick horney fubftance flmilar to 
a hard and thick cuticle : the narrow anterior and 
pofterior tendinous parts are alfo lined with a 
cuticle, but not fo flrong as the former : this 
horney "fubftance is gradually loft: at one end in a 
very thin cuticle, which lines the paflages of the 
cefophagus and inteftine for a little way ; and at 
the other end is alfo fimilarly loft in the mem- 
branous bag, or true ftoinach. 
The two large mufcles may be confldered as a 
pair of jaws, whofe teeth are taken in occaflonally, 
being fmall rough ftones or pebbles which the 
animal fwallows : and from the feeling on the 
tongue, it can diftinguilh fuch of thefe as are proper, 
from thofe which are fmooth or otherways unfit 
for the purpofe, which laft it inftantly drops out 
of its mouth. 
Some birds, with gizzards, have a craw or crop 
alfo, which ferves as a refervoir, and for foftening 
the grain ; but as all of them have not this organ, 
it is not to our prefent purpofe. 
There are other animals befides that clafs of 
birds, which mafticate their food in their ftomach, 
but their teeth are placed there by nature: crabs 
-and lobsters are of this kind. 
The gradation from gizzard to Jlomach is made 
by the mufcular tides becoming weaker and weaker, 
and the true ftomachic or gaftric part proportiona- 
Vol. LX1V. Sf bly 
