OF VERTEBRATE ANIMALS. 59 



of almost one genus, is perfectly symmetrical, i. e. that their 

 organs of sensation and motion are disposed in pairs on 

 the two sides of an axis or of a median line. They attain a 

 great size, and it is among them that we find the largest ani- 

 mals, which is owing to the bones that sustain the soft parts. 

 Their bodies are composed of a trunk, and with very few ex- 

 ceptions, of limbs. The trunk is upheld in its whole length 

 by the spine, a column formed of moveable vertebra placed 

 one on another, at one of whose extremities is the head; while 

 the other is generally prolonged into a tail. This column, 

 partly solid, is pierced by a canal which contains the spinal 

 marrow. The head is formed by the cranium which contains 

 the brain, and by the face which consists of the jaws and the 

 receptacles of the senses. The remainder of the trunk forms 

 one or two great cavities which contain the organs of the vege- 

 tative functions. In most of them, on the sides of the column, 

 are bony arches, or ribs, that protect the great splanchnic 

 cavity, and in the greater number, these ribs are articulated 

 in front with the sternum. The limbs never exceed in num- 

 ber two pairs, sometimes one, sometimes the other of these 

 are wanting, occasionally even both: in other respects their 

 forms are varied according to their destined relative move- 

 ments. 



The vertebratahave all two horizontal jaws, most commonly 

 furnished with teeth, hard bodies analogous to bones in their 

 chemical composition, and to horns in their mode of forma- 

 tion. In such as have no teeth (the bird and tortoise) we find 

 a true horny matter in place of them. In all the vertebrata, 

 the intestinal canal, extended from the mouth to the anus, and 

 presenting several enlargements, is furnished with secretory 

 glands viz: the salivary glands, the pancreas, and the liver. All 

 have arteries, veins, a heart variously formed and chyliferous 

 and lymphatic vessels. The blood is red. In one class only 

 (Fish,) are there branchia, in the remainder the respiratory 

 organ is lungs. Respiration is more or less great or perfect 

 according to the class. The organ for secreting bile, the liver, 

 receives in all the vertebrata, blood brought from the intes- 

 tines and the spleen by the vena-porta. They have all kid- 



