146 
ANATOMY AND PHYSIOLOGY 
gorge when handled. It is ejected by an antiperi- 
staltic movement of the viscus. When the crop is 
succeeded hy a gizzard, the food is soon urged, in 
small quantities at a time, into its opening, where it 
is subjected to the action of the teeth or horny 
ridges which cover its interior. The effect of this 
grinding process is so decisive, that it is in a short 
time reduced to a homogeneous pulp, which is called 
chyme. "When the gizzard is wanting chymifaction 
takes place in the crop. But the chyme does not 
attain the highest degree of elaboration, till it has 
been for a time in the chylific ventricle. Here it 
generally assumes a deeper colour, and the chyle is 
separated from it. The latter is a thick liquid of a 
whitish, brown, or greenish colour, and is found un- 
der a microscope to consist of minute globules. Its 
production is the grand object to which all the pre- 
vious processes tend, for it is the substance which 
forms the basis of all the nutritive fluids. An 
intermixture of bile has always been regarded as 
essential to its nature, and in the case of insects 
this ingredient has long been supposed to be supplied 
by what were formerly described as the bile- vessels. 
But several eminent physiologists have lately enter- 
tained some doubts on this subject, from observing 
that the so called biliary vessels empty themselves at 
a part of the canal behind the place where the chyle 
began to be absorbed; that their contents, when 
analysed, have little resemblance to gall, but consist 
in a great measure of uric acid ; and that many in- 
sects have other secreting organs which empty them- 
