ZOOLOGY. 377 



Hilaire, and Illiger, who have made quadrupeds their particular study ; 

 Temminck and Audubon, as ornithologists ; and Agassiz and Strack, 

 as ichthyologists ; who have extended the boundaries of this science, 

 by additions and corrections. The doctrine of a circular progres- 

 sion, in the arrangement and relation of animals, propounded princi- 

 pally by Mr. Macleay, is doubtless true in part ; and exhibits the 

 same complexity in the classification of animals, which we have 

 already noticed in the classification of the various branches of know- 

 ledge. In our own country, Dr. Godman has written ably on quad- 

 rupeds ; as Wilson, Nuttall, and Audubon, have done on birds ; and 

 Lea on shells. The invaluable collection of specimens made by 

 Mr. Peale, and now in the Philadelphia Museum, deserves, we think, 

 to be mentioned, even in this brief enumeration. 



We proceed to describe the Zoological system of Cuvier, under 

 the popular heads of, 1. Zoonomy ; 2. Mazology; 3. Ornithology; 

 4. Herpetology; 5. Ichthyology; 6. Arthrology; and, 7. Actinology. 



1. Under the head of Zoonomy, including Comparative Ana- 

 tomy, and Animal Physiology, we would treat of the general struc- 

 ture and functions of animals. Every organic body, whether animal 

 or plant, has a peculiar and definite form; which form it continues 

 to possess, although, by accretion and excretion, the materials of 

 which it is composed may be changed. All organic bodies have 

 also a peculiar structure ; consisting of solid fibres, or layers, enclos- 

 ing cellular, or tubular cavities, for containing the fluids necessary 

 for their nutrition ; the whole constituting what has been called an 

 areolar tissue, which is essential to every living body. Of this 

 tissue, there are, in animals, three different kinds ; the cellular sub- 

 stance, consisting chiefly of gelatine, which forms the various mem- 

 branes, cartilages, and vessels that contain fluids, and which, indu- 

 rated by earthy matter, forms the bones : the muscular fibre, con- 

 sisting chiefly of fibrine, and constituting the muscles, whose con- 

 tractile power is the immediate cause of animal motion ; and the 

 medullary matter, a pulpy substance, which chiefly constitutes the 

 brain, the spinal marrow, and the nerves, by whose agency the mind 

 acts on the muscles, to cause their contraction, and thus produce 

 voluntary motion. This effect is doubtless connected with galvanic 

 action ; but the manner and laws of this action are still a mystery. 



The growth of animals, is owing to the absorption and assimila- 

 tion of fluids, derived from their food: while their healthiness is 

 preserved by the exhalation or excretion of noxious and superfluous 

 matter. Having increased in bulk to their natural limit, animals 

 acquire an increase of density, in most of their parts, which pre- 

 cedes, and perhaps causes their decay and ultimate death. The 

 races would therefore become extinct without the power of repro- 

 duction ; which is perhaps the greatest mystery of life. The most 

 essential of the animal fluids, is the blood, or, in lower animals, the 

 sanies, which takes its place ; circulating through the system, and 

 supplying nutriment to every part, while it absorbs and removes any 

 superfluous or deleterious matter. The blood is elaborated from the 

 food, by means of the alimentary system: and, by means of the 

 respiratory system, it is purified and vivified during the process of 

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