32 



YRUTEBRATA. 



Frontal Bone. 



Parietal Hone. 



Oibil- 



Temporal 

 Bone 



Clavicle; 



Ilium. 



Carpus 



Metacarpus 



Phalanges 



Femur. 



Tibia. 



Fibula,. 



Metata 



Phalange* 



from one branch to another. Among swimming 

 animals, the tail is both rudder and oar. With 

 these exceptions and modifications, it will be re- 

 marked that the framework of the numerous 

 races belonging to this division are still formed 

 on one general plan, denoting a striking unity of 

 design. That this unity should be combined with 

 such infinite variety, is calculated to exalt our ideas 

 of the amazing resources of the Creative Mind. 



In the memb srs ^\ this division food is receh i 

 and in some degree prepared for digestion, by the 

 action of the jaws, the lower of which opens 

 perpendicularly. In general, these are armed 

 with bony projections, called teeth, which cut or 

 grind the food.. These are of great importance, 

 Dot only in the economy of animals, but they are 

 an essential guide in classification. The cutting 

 teeth, called incisors, occupy the front of the 

 mouth : the canines, or carnivorous teeth, arc 

 conical, four in number, two on each side of the 

 mouth. The molars, or grinding teeth, are set 

 back in the jaw, and are extremely various in 

 form. They are very important, however, in in- 

 dicating the habits and internal structure of ani- 

 mals. It is said that Cuvier could instantlv dc- 

 termine the character of any animal — its habits, 

 food, structure of the stomach, form of the limbs — 

 of which lie could he furnished a set of the teeth. 

 In this way the nature of many fossil animals has been determined. In general, it may be said 

 that the molars of flesh-eating animals are pointed or conical at the summit, while those of rumi- 

 nants and rodents are more flat and even. In man, we find examples of all these kinds of teeth : 

 in some animals, as the ox and horse, the canines are entirely wanting. While some classes of 

 vertebrata are thus furnished with teeth, they are not found in others, birds and tortoises having 

 their jaws incased in a horny beak. The food received into the body of the animals we are dc- 

 scribing passes from the mouth through a tube into a sac, called the stomach, where it undergoes 

 certain chemical changes, and receives various secretions from the body. It then enters into a 

 lengthened membraneous tube called the intestine, the sides of which arc studded with innumer- 

 able little vessels, by which the nutritious portion of the food is taken up and conveyed into the 

 veins to form blood, the useless portion being rejected. 



Before the supply of nutritious matter which we have just seen poured into the veins can he 

 made available for the support of the body, it must undergo some important changes. These arc 

 sted by the admixture of oxygen, derived generally from the atmosphere; but in the case of 

 ashes, from the water. To understand in what manner this admixture takes place, we must glance 

 a moment at the circulatory s;/st<n). All the animals of this division are copiously supplied with 

 a fluid essential to their existence, called blood, from which it is believed all other parts of the 

 body, even the most solid, arc originally formed, and by which they are increased and supported. 

 This fluid ceaselessly circulates through two series of vessels, ramifying with inconceivable minute- 

 ness to every part of the animal. In the one set, called veins, receiving the blood after it has per- 

 formed its renovating office, we have said that it mixes with foreign matter from the digested 

 food; thus supplied, it is carried to the heart, a large hollow muscle, which alternately contracts 

 and expands without intermission, by which motions it is received and thrown forward in regular 

 pulsations. 



Hence, in whole or in part, it is carried, in those animals which breathe air, to the lungs — a 



SKELETON OF A MAN. 



