8 NATURAL HISTORY. 



The first point, then, which we should have to study 

 in connection with any animal is its actual structure 

 that is to say, its external characters and the form and 

 arrangement of its internal organs. The study of the 

 configuration of animals constitutes that department of 

 natural history which is technically known as MORPHOLOGY, 

 or the science of Form in other words, what is generally 

 understood as ANATOMY. 



Secondly, having acquired an acquaintance with the 

 structure of an animal, it is next necessary to study its 

 vital functions, to discover the uses of its internal organs, 

 and the way in which they work, and to investigate the 

 purposes subserved by its various parts when in action. 

 This constitutes the department of natural history known 

 as PHYSIOLOGY, or the science of Function. 



In the third place, our knowledge of an animal is 

 very incomplete, unless it embraces an acquaintance with 

 those changes which it undergoes in passing from the 

 germ to the adult condition. The study of these con- 

 stitutes the important branch of zoology known as 

 EMBRYOLOGY, or the science of Development. 



In the fourth place, it is necessary to know of each 

 species of animals what are its relations to the world 

 we live in. We have to inquire where the species now 

 lives, what are the conditions under which it exists, and 

 so forth; and the study of these points constitutes a 

 special branch of natural history, which is termed the 

 GEOGRAPHICAL DISTRIBUTION OF ANIMALS. 



Again, fifthly, we should find that each species of animals 

 has had a history, extending backwards into the past; 

 and we should have to study the time of the first 



