50 



ON THE PLACE OF MAN IN THE SCALE OF BEING. 



it, is never at all comparable with that which we ordinarily find in the Mol- 

 lusca. Thus, the liver, which in the Oyster forms a large part of the whole 

 substance, is often scarcely recognizable as such in the Insect; and the intes- 

 tinal tube seldom makes many convolutions in its course from one extremity 

 to the other. The blood is usually white, as in the other Invertebrated classes : 

 but it contains a larger number of corpuscles than are seen in that of most of 

 the Mollusca. The temperature varies to a certain degree with that of the 

 atmosphere; but many Insects have the power of generating a large amount of 

 independent heat, which is strictly proportionable to the quantity of oxygen 

 converted by them into carbonic acid in the respiratory process. All the ac- 

 tions of the Articulata are performed with great energy ; and, at the time of 

 the most rapid increase of the body, the demand for food is so great, that a 

 short suspension of the supply of aliment is fatal. Many of them are capa- 

 ble, however, of being submitted to the influence of very extreme temperatures, 

 with little permanent injury. 



19. The adjoining figure, which displays the muscular apparatus of the 

 interior of the body of a Cock-chafer, will give an idea of its complexity and 

 variety, and of the large portion of the trunk which is occupied by it ; and 

 will also show the division of the skeleton into segments, the number of 

 which in Insects is limited to thirteen. These are nearly equal and similar 

 to each other in the Larva ; but, in the perfect Insect, the three behind the 

 head are united into the thorax, to which the legs and wings are attached ; 

 and the remainder form the abdomen, which has little concern in locomotion. 



Fig. 4. 



it 



Section of the trunk of Melolontha vulgaris, (after Strauss-Durckheim,) showing the complexity of the 

 Muscular system. The first segment of the thorax (2) is chiefly occupied by the muscles of the head, 

 and by those of the first pair of legs. The second and third segments (3 and 4) contain the very large 

 muscles of tin; wings, and those of the other two pairs of legs. The chief muscles of the abdomen are 

 the long dorsal and abdominal recti, which move the several segments one upon the other. 



6. General characters of Veriebrata. 



20. In none of the three preceding divisions of the Animal kingdom, does 

 the Nervous System attain such a degree of development, as to give it that 

 predominance in the whole fabric which it evidently possesses in VERTE- 

 BRATA. In the Radiata and Mollusca, its functions are obviously restricted to 

 the maintenance of the nutritive operations ; and to the guidance of the ani- 

 mal, by moans of its sensory endowments, in the choice of food, as well as 

 (in some instances) in the search for an individual of the opposite sex : in the 



