CHAPTER III. 



THE ELEMENTS OF STRUCTURE. 

 (Morphology.) 



Animals may be studied alive or dead, in regard to their 

 activities or in regard to their parts. We may ask how they 

 live, or what they are made of; we may investigate their 

 functions or their structure. The study of life, activity, 

 function, is physiology ; the study of parts, architecture, 

 structure, is morphology. 



The first task of the morphologist is to describe structure 

 (descriptive anatomy) ; the second is to compare the parts 

 of one animal with those of another, discovering structural 

 resemblances or homologies (comparative anatomy) ; the 

 third is to generalise, to formulate the " principles of 

 morphology " or the laws of vital architecture. But in none 

 of his tasks, least of all in the last, can he help being or 

 trying to be a physiologist and an evolutionist also. 



But just as the physiologist may investigate life or activity 

 at different levels, passing from his study of the animal as 

 a unity with habits and temperaments, to consider it as an 

 engine of organs, a web of tissues, a city of cells, and a 

 whirlpool of living matter; so the morphologist has to 

 investigate the form of the whole animal, then in succession 

 its organs, their component tissues, their component cells, 

 and finally, the structure of protoplasm itself. The tasks of 

 morphology and of physiology are parallel. 



Morphology thus includes not only the description of 

 external form, not only the anatomy of organs, but also that 

 minute anatomy of tissues and cells and protoplasm which 

 we call histology. Moreover, there is no real difference 

 between studying fossil animals which died and were buried 



