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146 when handled. It is ejected by an antiperistaltic movement of the viscus. When the crop is succeeded by 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 under a microscope to consist of minute globules. Its production is the grand object to which all the previous 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 entertained 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 insects have other secreting organs which empty