INTRODUCTION. , vii 



ARRANGEMENT OF ANIMALS. 



No arrangement of animals can be perfect ; first, because we do not know that we are 

 acquainted with all the species ; secondly, because there are many species of which we know 

 very little ; and thirdly, because of those which we know best, the greater part are known 

 as more or less domesticated ; and we are consequently unable to separate the natural parts 

 of their characters from the artificial. The system of the late Baron Cuvier possesses sim- 

 plicity as well as some other advantages, and therefore, in brief outline, we shall nearly 

 follow it, though in different language, and with such alterations as may seem more suited 

 for ordinary readers. The fundamental principle of that system may be said to be the greater 

 or less development of the principle of life, as indicated by the brain or central part of the 

 cerebral or nervous mass being both more produced and more localised, or, if the expression 

 may be allowed, more or less concentrated ; and in proportion as life is thus more developed, 

 and, according to our ordinary mode of expression, more complex, or has a higher degree 

 of organisation, it is also more easily deranged by mechanical injuries, and parts that 

 are mutilated or destroyed, are not so easily restored or replaced. A wound in the human 

 body always leaves a scar, unless where healed by what is called " the first intention," or 

 without inflaming or granulating : and though so healed, it leaves a raphe or seam if it be large. 

 When a nail is torn off the human finger, it is not often replaced by one equally perfect ; and 

 if even the tip of a finger is cut off', it does not grow again. The parts, within certain limits, 

 have the power of preservation and repair j but the production of that which we call the more 

 perfect animal appears to be the effect of one united and concentrated energy, which cannot be 

 made to act again in the reproduction of a single organ. As we descend in the scale, and the 

 energy of life is less concentrated, the power of reproduction increases. The leg of a frog, or the 

 claw of a crab, will grow again; and when we descend still lower, to some of the small form- 

 less animals which inhabit the water, we find that almost any part can be reproduced , and 

 that the species may be multiplied by mechanical division, as the segments grow to perfect 

 animals. There is not, however, any gradual chain traceable from the one to the other ; all 

 species are distinct, and we can only form larger groups by means of some general charac- 

 ters, and leave the particular characters to the smaller subdivisions. 



The most important and general, as well as the most obvious distinction, is that of 

 Verlebraled and Inverlebratcd animals ; or, animals which have spinal columns or back-bones, 

 and animals which have not. To avoid repetition, and insure brevity, we shall take these in 

 their order, without contrasting the one with the other. 



VERTEBRATED ANIMALS. 



These have the central mass of the nervous system inclosed in a case of bone, com- 

 mencing anteriorly in the skull, and continued through the spinal column, which consists of 

 a greater or smaller number of pieces or vertebrae, (but always of the same number in the 

 same species,) variously articulated, or jointed together, according to the strain that they have 

 to bear, and the motions they have to perform ; but always well secured against dislocation, 

 and so formed that the nervous mass which passes through them can sustain no injury in 

 their ordinary and natural motions. This column may be considered as the centre or basis 

 of the organisation to which all the other bones which support the softer parts are articu- 

 lated. To the anterior extremity of the column are united the bones of the face and mouth, 

 the latter consisting of two jaws, placed the one above the other, and having their principal 

 motion in the elevation and depression of the under jaw, and the jaws variously furnished 

 with teeth according to the habits of the species and the nature of their food. The other 

 extremities, or limbs, never exceed four, are sometimes only two, and sometimes wholly 

 Avanting. They are more or less intimately articulated to the vertebral column, according 



