COMPARATIVE ANATOMY. 



which are termed the lips of insects are 

 two bodies, of which one is placed above 

 or in front of the jaws, and the other be- 

 low or behind them. The palpi or feel- 

 ers are articulated to the jaws. All in- 

 sects which have jaws, possess the power 

 of masticating hard animal and vegetable 

 substances ; for these parts are of a firm 

 horny texture, and in many cases are very 

 large, when compared with the size of 

 the animal. 



The locust (grylli,) the dragon-fly 

 (libellula,) the beetles, and particularly 

 the lucauus cervus, or stag-beetle, and 

 the staphylinus maxillosus, are examples 

 in which the jaws are very large and 

 manifest, and often possess denticulated 

 edges. All the genera of the following 

 order have jaws ; viz. the coleoptera, 

 orthoptera, neuroptera, and hymenopte- 

 ra. The insects of the remaining orders 

 derive their nourishment chiefly from li- 

 quids ; which they get either from ani- 

 mal or vegetable substances by means of 

 a spiral and tubular tongue, or soft pro- 

 boscis, as in the lepidoptera ; with a broad 

 opening, admitting of extension and 

 retraction (the hemiptera ;) or a horny 

 pointed tube, containing sharp bristly 

 bodies internally (the diptera and ap- 

 ?era.) 



The stomach of the bee is a transparent 

 membranous bag, in which the nectar of 

 the flowers is elaborated and converted 

 into honey. The animal vomits it up from 

 this reservoir, and deposits it in the hive. 

 The stomach of the crab and lobster is 

 a very singular organ. It is formed on a 

 bony apparatus, in short, a species of 

 skeleton, and does not therefore collapse 

 when empty. To certain parts of this 

 bony structure, round the pylorus, the 

 teeth are affixed. Their substance is ex- 

 tremely hard, and their margin is serra- 

 ted or denticulated ; as they surround the 

 tube, near the pylorus, nothing can pass 

 that opening without being perfectly 

 comminuted. These bones and teeth are 

 moved by peculiar muscles. 



In those mcHlusca, which possess jaws, 

 these parts are fixed in the flesh of the 

 animal, as there is no head to which they 

 can be articulated. They are two in num- 

 ber in the cuttle-fish, are composed of a 

 horny substance, and resemble exactly 

 the bill of a parrot. They are placed in 

 the centre of the lower part of the body, 

 and are surrounded by the tentacula, 

 which enable the animal to attach itself to 

 any object. By means of these parts, the 

 shell-fish, which are taken for food, are 

 completely triturated. The common snail 



and slug have a single jaw, semilunar in its 

 form, and denticulated. The tritonia has 

 two jaws, which act like the blades of a 

 pair of scissars. The other mollusca 

 possess no organs of this kind, but have, 

 in some instances, a sort of proboscis ; 

 as the buccinum, murex, voluta, doris, 

 scyllsea, &c. 



In the worms, properly so called, there 

 are sometimes hard parts, forming a kind 

 of jaws or teeth ; thus in the nereis, the 

 mouth possesses several'calcareous pieces. 

 The ophrodite (sea-mouse) has a probos- 

 cis, furnished with four teeth, which it 

 can extend and retract at pleasure. With- 

 in the mouth of the leech are three semi- 

 circular projecting bodies, with a sharp 

 denticulated edge : by this apparatus the 

 animal inflicts its wound of the well known 

 peculiar form in the skin. 



The teeth of the echinus (sea-hedge- 

 hog) are of a very singular arrangement ; 

 a round opening is left in the shell for the 

 entrance of the food ; a bony structure, 

 on which five teeth are placed, fills up 

 this aperture; and as these parts are 

 moved by numerous muscles, they form 

 a very complete organ of mastication. 



The stomach of the vermes is, in gene- 

 ral, a membranous bag, but in some cases 

 its structure is more complicated. The 

 helix stagnalis and the onchidia have 

 gizzards. The aplysia has three strong 

 muscular stomachs, provided with pyra- 

 midal bony processes. The latter struc- 

 tures, together with those of the lobster 

 and crab, present a new analogy, as Cu- 

 vier has observed, between the mem- 

 branes of the intestines and the integu- 

 ments of the body. This is particularly 

 strengthened by the annual shedding of 

 the lobster's teeth, when its crustaceous 

 covering falls off. 



The bull* lignaria has a very powerful 

 stomach, containing three hard calcareous 

 shells, by which the animal is enabled to 

 bruise and masticate the other testacea 

 on which it feeds. 



ON THE INTESTINAL CANAL. 



The intestinal canal (which is the most 

 common part in the whole animal king- 

 dom after the stomach) is distinguished in 

 the mammalia by two peculiarities, which 

 depend on the mode of nutrition. It is 

 comparatively shorter in carnivorous ani- 

 mals, and there is also in these less dif- 

 ference, to external appearance, between 

 the small and the large intestine than in 

 the herbivora. Yet these rules are not 

 without their exceptions ; for the seal has 



