It examines into the circumstances which modify their 

 sensations and perceptions, and discovers the sources of 

 their peculiar instincts and habits. It describes the va- 

 rious modes in which the functions of Digestion, Circula- 

 tion, Respiration, and Secretion, are performed in the lower 

 classes of animals, and the duty assigned to each part of 

 their structure in the performance of these functions. It 

 points out the connexion which exists between the forms 

 and mechanism of the various parts and the particular cir- 

 cumstances of each species, and the influence of their inter- 

 nal organization over all the phenomena they exhibit. It 

 unfolds to our contemplation the inexhaustible resources 

 of Nature in the means employed for the propagation of the 

 species, from the simple fissiparous generation of Animal- 

 cules, or the almost equally simple gemmiparous mode of 

 Zoophytes, to the highly complicated viviparous birth of 

 Quadrupeds. In thus investigating the various functions 

 of the animal economy, in all their different stages of 

 simplicity and complication, it determines the true nature of 

 animal life, and the conditions essential to its existence, and 

 discovers the characteristic properties which distinguish 

 animals from the beings belonging to the Vegetable and 

 Mineral Kingdoms. And by the successful applications of 

 the principles of chemical and mechanical science to the 

 explanation of their complicated functions, it shows that, 

 notwithstanding the disturbing forces of the animal econo- 

 my, which have hitherto defied all attempts at generaliza- 

 tion, the true solution of all vital phenomena and the laws 

 of organized beings are to be looked for in those magnifi- 

 cent arrangements which embrace the whole system of the 

 visible universe. 



The term Zoology (derived from the Greek words &ov 

 an animal, and ^oyo; a discourse,) has long been applied 

 to that branch of Natural History which treats of ani- 

 mals. It chiefly considers animals in their entire and 

 living state, and describes their external forms and dis- 

 tinguishing characters, the history of their life, and the 

 principles of their scientific arrangement. It points out 



