GENERAL REVIEW OF LIVING BEINGS. 



19 



THE ANIMAL KINGDOM. 



DIVISION I VERTEBRATA, SUBDIVIDED INTO FOUR CLASSES. 



, ,, f Man and Beasts, with warm blood; heart with two ventricles; females sucklin" their youne with milk, secreted in breasts 



1. Mammalia { . [ . , ,, ... ., . " ^ .. 



I or mammce; viviparous, excepting the Monotremata, wnicn are either oviparous or ovo-viviparous. 



. ( Birds, with warm blood; heart with two ventricles; no mammae; oviparous; body covered with feathers, and organizei' 



■ "^^ (for flight. 



„ T) f Reptiles, with cold blood ; heart with one ventricle ; having lungs, or sometimes only gills or branchiae ; oviparous, or 



I ovo-viviparous ; generally amphibious. 



. p f Fishes, with cold blood; heart with one ventricle; no lungs, but breathing by branchiae; generally oviparous; body or" 



{ ganized for swimming. 



DIVISION II.— MOLLUSCA, SUBDIVIDED INTO SIX CLASSES. 

 C Cuttle-fishes, having the mantle furnished with a shell, and united under the body, forming a muscular sac; head con- 



1. Cephalopoda... J nected with the mouth of the sac, and crowned with long and strong fleshy limbs, for walking on, and seizing their prey; 



(^ with two large eyes; and two gills placed in the sac. Sexes separate. 



2. Ptekopoda Marine animals without feet; with two fins, placed one on each side of the mouth; head distinct; hermaphrodites. 



„ p f Snails or Slugs, and Limpets, with a distinct head; crawhng on a fleshy disc; very seldom with fins; generally with a 



( shell ; tentacula from two to six. 

 . , f Aquatic animals, generally with a bivalve or multivalve shell; without an apparent head or lirabs; mouth concealed be- 



) twecn the folds or in the bottom of the mantle ; hermaphrodites ; branchiae external ; incapable of locomotion, 

 r T) J Marine Animals, without a head ; having two fleshy arras, furnished with numerous filaments ; bivalve shells; incapable 



( of locomotion. 

 ^ r' ( Barnacles, inclosed in a multivalve shell; with numerous articulated limbs or cirrlii, disposed in pairs; incapable of loco- 



6. LIKRHOPODA -[ . . ' r r ' r 



(^ motion. General structure approaching to the articulated animals. 



DIVISION IIL— ARTICULATA, SUBDIVIDED INTO FOUR CLASSES. 



f Worms, generally with red blood; without limbs; usually hermaphrodites, perfect or reciprocal; body soft; more or less 



1. Annelides J. elongated, and divided into numerous segments; circulation double, with one or more hearts or fleshy ventricles; respir- 



(^ ing generally through branchia; ; sometimes dwelling within membraneous, horny, or calcareous tubes. 



C Marine Animals, with a crustaccous envelope, having articulated limbs attached to the sides of the body; blood white; 



2. Crustacea ^ always with articulated antennae or feelers in front of the head, and generally four in number; distinct organs of circula- 



(^ tion; respiring through branchiae. 

 „ A „„.,,„„„ f Spiders, with the head and breast united in a single piece, and with the principal viscera situate in a distinct abdomen, 

 ( behind the thorax; without antenna;; oviparous. 



4. Insecta Insects, divided into three distinct parts, the head, thorax, and abdomen; always with two antennae, and six feet. 



DIVISION IV.— RADIATA, SUBDIVIDED INTO FIVE CLASSES. 



f Sea- hedgehogs, and Sea-stars, with distinct viscera and organs of respiration; with a partial circulation; often with a 

 1. EcHiNODEnMATA< kind of skeleton, armed with points or moveable spines; destitute of head, eyes, and articulated feet; nervous system 



( indistinct ; organs of motion extremely imperfect. 

 (J P J Intestinal Worms, with no distinct organs of circulation oi respiration; body generally elongated, and organs arranged 



1^ longitudinally; without head, eyes, or feet. 



3. AcALEpH.E Medusae, or Sea-nettles, without organs for circulation or respiration; with only one entrance to the stomach. 



4 P >LTPr / Small Gelatinous Animals, with only one entrance to the stomach, surrounded with tentacula; generally adhering together 



( and forming compound animals. 

 t Animalcules, or Minute Microscopic Animals, found in fluids, or vegetable infusions. As theii- internal structure is but 



5. Infusoria -? httle known from their extreme smallness, this class will probably be found hereafter to contain animals which ought to 



(_be placed in some of the higher divisions. 



SECT. XI. — GENERAL REVIEW OF LIVING BEINGS CONTINUED. 



Subordination of Characters — Imaginary Chain of Beings — Circular Hypotheses. 



The preceding Tables exhibit the primary and secondary divisions of Living Beings, 

 hi the course of this work, we shall describe the organs and functions from which their 

 characters are derived. At present let us consider somewhat further the laws of their 

 subordination and co-existence. 



Upon iuTestigating the internal structure of the entire Animal Kingdom, certain 

 beings are discovered, consisting of a stomach isolated from every other organ, without 

 visible nerves or muscles, without a heart or vessels, and destitute of a brain and organs 

 of sense. We are, therefore, led to consider the stomach as the most essential cha- 

 racter. The most variable organs must be regarded as of the least importance ; and 

 wc thence conclude that the nerves, muscles, heart, lungs, and brain, are subordinate 

 cliaracters. 



But on investigating the more complex animals provided with all the organs just 

 enumerated, and upon studying the gradual progress of their development, it is found 

 that the heart is the first formed of the organs, or at least it is the first visible orf^an, 

 and that one in which the vital action is most evident. Upon examining the structure 

 of monstrous beings, we observe that the heart can exist without the other organs 

 much oftener and more perfectly than they can exist without the heart. Again, when 

 we observe an animal already bi-ought to light, and increased in magnitude, we see the 

 organs of sense, the brain, and the greater number of muscles, suspend their functions 

 in a periodical sleep; wc see tlio lungs themselves sometimes cease to act for a short 

 space of time; while the heart continues to beat as long as Ufe exists. For all these 



reasons, the heart appears to be the most important organ among the higher ani- 

 mals. 



It must be admitted, however, that many difficulties prevent us from determining 

 precisely which of the five organs, essential to the hfe of a vertebrated animal, is the 

 most important, when we see the animal healthy, full grown, perfectly formed, each 

 organ exactly performing all its functions, and the entire being in the fiJl exercise of 

 all its powers. It has been already explained that the whole of the organs presuppose 

 a stomach which nourishes them. The lungs and gills cannot exist without the brain ; 

 the brain in its turn requires the action of the heart; and the heart itself cannot per- 

 form its functions without the aid of the spinal marrow and of the lungs, which are 

 ruled by the brain. All the organs form a mutually-connecting bond of union. It is 

 true that if we examine in detail any one of the subordinate organs, it appears to 

 have more need of the blood than of the nerves, and that it can exist longer without 

 the action of the brain than of the heart. But if we contemplate any part of the 

 complicated wheelwork essential to Life, it is found to be reciprocally connected, 

 and this even in the most varied and intricate manner. Yet, when we see the heart 

 commencing to beat before the stomach and lungs are in action, — when it is observed 

 to throb during the absence of respiration, or after it has altogether ceased, — when 

 we see that mutilations of the brain do not always produce instantaneous death, 

 while the destruction of the spinal marrow speedily causes the heart to cease its move- 

 ments, — we have sufficient grounds for supposing that the circulation of the blood is 

 the primary essential condition of existence among any of the higher animals. For 

 these reasons, in arranging the numerous subjects of the Animal Kingdom, the spinal 

 marrow, which appears to govern the action of the heart, must be considered as the 



