DESCRIPTION OF PARTS. 15 



rarifying the air in its interior ; in consequence of which, fluids rise in it as in a pump. 

 We have in this case an instance of a modification of an organ of the simplest kind, by 

 which, however, the entire function is changed ; passing from a digestive function to a 

 transferring one, or one more immediately subservient to the mouth. 



The gizzard is the next organ, and may be distinguished from the crop by its peculiar 

 apparatus for mastication : its internal surface is studded "with teeth or spines, or horny 

 ridges ; " the organ, therefore, is eminently fitted for performing a perfect comminution of 

 the matters received into it. It completes, in this respect, what has been performed but 

 imperfectly. It performs a function somewhat analogous to that of rumination in the 

 herbivora. All the insects which feed upon hard substances, those which might be regarded 

 as nearly indigestible, are provided with a strong muscular gizzard, furnished with a 

 masticating apparatus. 



The stomach, or that part' in which we first observe the food reduced to a pulpy mass, 

 and first exhibiting a chylous appearance, is bounded above by the gizzard, and below by 

 a constricted portion of the canal, which receives a bundle of vessels that give it an ana- 

 logy to the liver of vertebrated animals, and in fact it is strictly the hepatic organ of in- 

 sects. The stomach is of an oval shape, or an elongated oval : it has been denominated the 

 chylific ventricle by M. Leon Dufour. Its capacity is considerable : its surface is lined by 

 a mucous membrane, and it is sometimes studded over with little mucous cysts or bags, 

 which secrete a solvent fluid similar in composition and use to the gastric fluid of the 

 higher animals. The organ, in order to increase the extent of surface, is frequently con- 

 stricted, and also twisted upon itself, so as to form many circumvolutions, and hence it is 

 quite variable in shape in the different orders of insects : its inner surface, however, is 

 always villous. 



From the stomach outwards or downward, the canal becomes narrower, or passes along 

 with a diminished calibre ; but as there are still enlargements or dilatations in its course, 

 anatomists speak of a duodenum, ileum, caecum, colon and rectum. But this is regarded by 

 many as an unnecessary multiplication of names, inasmuch as it is extremely difficult to 

 recognize the parts which are thus designated. The beginning of this part of the canal, 

 however, is indicated by a constriction and the existence of a sphincter muscle, as well as 

 by the junction below of the hepatic vessels. The tube is generally short, rarely exceeding 

 the length of the body : sometimes it is inflated into an ovoid sac rather abruptly. 



In following out the distinction of parts in the intestinal canal, we may recognize the 

 existence of a colon, or what corresponds to the large intestines of the higher animals, by 

 the character of the alimentary ball ; for the food, after having passed the stomach and 

 through the narrowed part of the canal posterior to the stomach, loses its viscidity, and 

 becomes more or less dry and compacted into the form of an excrement, showing by its 

 condition that the nutrient matter has been extracted from it. Here is also a valve to guard 



