COMPARATIVE ANATOMY. 



elucidating the structure or functions of 

 the human body. 



It is necessary for us to make a few 

 remarks on the classification of the ani- 

 mal kingdom* as the terms employed in 

 the following article differ occasionally 

 from those of the Linnaean system, which 

 has been hitherto chiefly used in this 

 country ; and, independently of this cir- 

 cumstance, such of our readers, as have 

 not particularly attended to the study of 

 natural history, may derive assistance and 

 information from a short sketch and ex- 

 planation of the arrangement of animals 

 according to their anatomical structure, 

 with an enumeration of the chief genera 

 in each order. 



That the Linnaean system is exposed to 

 numerous and well grounded objections, 

 and that in many instances it disregards 

 anatomical structure, which shouldVorm 

 the basis of a natural classification, will 

 be readily allowed by the most sanguine 

 admirers of its illustrious author. Yet it 

 must be remembered, that the general 

 adoption of this method renders it desira- 

 ble to deviate from it in as few instances 

 as possible ; since the introduction of new 

 orders and names must necessarily create 

 difficulty and confusion in the study of 

 the science. The French zoologists, 

 whose successful labours in the advance- 

 ment of natural history must be acknow- 

 ledged with every due tribute of respect, 

 have carried the rage of innovation too 

 far, in the universal rejection of the Lin- 

 nsean method, and the unnecessary multi- 

 plication of new orders and genera. The 

 defects or errors of any system could not 

 cause so much perplexity and inconve- 

 nience, as the want of a generally receiv- 

 ed standard, and the unlimited licence, 

 in which every individual indulges, of 

 fabricating new classifications and arrange- 

 ments. To judge by some recent works, 

 we should be led to suppose, that the 

 merit of a systematic arrangement of ani- 

 mals does not consist in the simplicity 

 or intelligibility of the system ; but is in 

 proportion to the number of newly -creat- 

 ed terms. 



Animals may be distributed into two 

 grand divisions : those which have a ver- 

 tebral column, and red blood : and those 

 which have no vertebrae, and are white 

 blooded. 



In the former division there is always 

 an interior skeleton ; the chief support of 

 which is the column of vertebrae, a spinal 

 marrow contained in the vertebral canal; 

 never more than four members, of which 

 one or both pairs are wanting in some 



instances. The brain is contained in a 

 cranium : there is a great sympathetic 

 nerve; five senses; two moveable eyes ; 

 and three semicircular canals in the ear. 

 The circulation is performed by one mus- 

 cular ventricle at least. There are lym- 

 phatic as well as blood vessels. Thejuws 

 being placed horizontally, the mouth is 

 opened by their moving from above down- 

 wards, or from before backwards. There 

 is a continuous alimentary canal, ex- 

 tending from the mouth to the anus, 

 which is always placed behind the pelvis; 

 peritoneum; liver, spleen, and pancreas; 

 two kidneys, and renal capsules ; and two 

 testicles. 



The vertebral animals are subdivided 

 into warm and cold-blooded. 



Warm blooded vertebral animals have 

 two ventricles in the heart, and a double 

 circulation ; and breathe by means of 

 lungs. The cranium is comple'.ely filled 

 by the brain. The eyes are closed by eye- 

 lids. The tympanum of the ear is hollow- 

 ed out of the cranium, and the labyrinth 

 is excavated in the bone. Besides the 

 semicircular canals, the ear lias a coch- 

 lea. The nostrils communicate with the 

 fauces, and allow the passage of air into 

 the lungs. The trunk is constantly fur- 

 nished with ribs. 



In cold blooded vertebral animals, the 

 brain never entirely fills the cranium. The 

 eyes seldom possess moveable eye lids. 

 When the tympanum exists, it is on a 

 level with the surface of the head. There 

 is no cochlea. The different parts of the 

 ear are connected but loosely to the cra- 

 nium. 



The division of warm blooded ani- 

 mals contains two classes; Mammalia 

 and Birds. 



The mammalia are viviparous, and 

 suckle their young, from which circum- 

 stance the name is derived. They have 

 an uterus with two cornua : and the male 

 has a penis. 



There are two occipital condyles, con- 

 necting the head to the atlas : never less 

 than six, nor more than nine cervical ver- 

 tebrae: a very complicated brain ; four 

 ossicula auditus, and a spiral cochlea. 

 The skin covered with hair. A muscu- 

 lar diaphragm separates the chest and 

 abdomen. There is an epiglottis. The 

 lower jaw only moves. The fluid in the 

 lacteals is white, and passes through 

 several conglobate glands. Th?re is an 

 omentum. 



Blumenbach establishes the following 

 orders in this class : 



