THB RABBIT. 11 



aspect wo specially consider the form and structure, relative 

 position and mutual relations of the various parts which 

 collectively make up the animal, and the changes which 

 these undergo during development ; we compare one animal 

 with another, seek for underlying similarities among the 

 obvious differences they present. This kind of study 

 constitutes what is called Morphology, and it is divided into 

 three chief branches Anatomy, or the study of the parts 

 (members) of an animal ; Histology, or the study of the 

 tissues or fabrics of which the members are composed ; and 

 Development, or the study of the changes by which members 

 and tissues come to be what they are. The second point of 

 view is that of the functions or activities of the parts of the 

 animal, which from this point of view are organs rather 

 than members. Here, taking anatomy and histology as 

 our basis, we seek to learn what part all these structures 

 play in the life of an animal. This is Physiology. 



18. Homology and Analogy. The difference of view of 

 the morphologist and physiologist is most clearly seen when 

 the comparison of two different animals is in question. The 

 former looks keenly for similarities in origin and structure 

 between organs which may serve very different functions in 

 the two cases ; the latter is more interested in seeing how 

 similar necessities of life lead to organs of different origin 

 and structure being adapted to the same function in the 

 two cases. Organs of the former kind in different animals 

 are said to be homologous, those of the latter kind are 

 analogous. We shall, in the course of our work, come 

 across examples of organs which are homologous with one 

 another, but not analogous, others which are analogous, 

 but not homologous, and many which are both. 



19. Distribution. Besides Morphology and Physiology 

 there is a third branch of Biology Distribution which we 

 shall barely touch. This may be called the geography and 

 ancient history of living things. 



