INTRODUCTION. 



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 

 jr— 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 in- 

 terior 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, «S:c. 

 This apparatus is absent in 

 sucking insects and those which 

 live on soft substances, such as 

 the pollen of flowers, &c. 



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 papillae, 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 casca, and 

 larger and less numerous. 



They have been considered as secretory organs, answering to 

 the pancreas in vertebrate animals. 



W 



-Digestive apparatus of Carabus auratus. 



