[1] _Ganglion_--a mass, literally a knot, of nervous matter. In its most complicated form the alimentary canal is composed of an _oesophagus_, or gullet, of a crop, of a gizzard, of a chylific ventricle or stomach, a small intestine, a large intestine, divers appendages, salivary, biliary, and urinary glands. The oesophagus is often not wider than a hair, and part of it in many species is enlarged into a pouch, which is called the crop, because it occupies the same position, and performs analogous functions with that organ in birds. It is enough to say that the food remains there some time before passing on to the other parts of the intestinal canal, and undergoes a certain amount of preparation. It is in the gizzard, when one exists, that the food, separated by the masticatory organs of the mouth, undergoes another and more complete grinding. Its structure is suited to its office. It is, in fact, very muscular, often half cartilaginous, and strongly contractile. Its interior walls are provided with a grinding apparatus, which varies according to the species, and consists of teeth, plates, spines, and notches, which convert the food into pulp. It only exists among insects which live on solid matters, hard vegetables, small animals, tough skin, &c. This apparatus is absent in sucking insects and those which live on soft substances, such as the pollen of flowers, &c. [Illustration: Fig. 10.--Digestive apparatus of Carabus auratus.] The chylific ventricle or stomach is never absent; it is the organ which performs the principal part in the act of digestion. Two kinds of appendages belong to the chylific ventricle, but only in certain families. The first are papillæ, in the form of the fingers of a glove, which bristle over the exterior of this organ, and in which it is believed that the food begins to be converted into chyle. The second are cæca, and larger and less numerous. They have been considered as secretory organs, answering to the pancreas in vertebrate animals. Fig. 10, which represents the digestive apparatus of _Carabus auratus_, a common beetle, presents to the eyes of the reader the different organs of which we are speaking. A is the mouth of the insect, B the oesophagus, C the crop, D the gizzard, E the chylific ventricle, F and G the small and large intestines, and H the anus. It is not necessary to consider the other parts of the alimentary canal in insects, but only to refer to some of the appendages of this apparatus. The salivary glands pour into the digestive tube a liquid, generally colourless, which, from the place where it is secreted, and its alkaline nature, corresponds to the saliva in vertebrate animals. It is this liquid which comes from the tongue of sucking insects in the form of drops. These glands are always two in number. Their form is as variable as complicated. The most simple is that of a closed flexible tube, generally rolled into a ball, and opening on the sides of the oesophagus.