8 PHYSIOLOGY AND MORPHOLOGY OF ANIMALS. 



field of zoology is far too extensive; we can occupy but 

 a small part. 



SECTION II. 



DEFINITION OF ZOOLOGY AND THE SCOPE AND LIMITS 

 OF THIS COURSE. 



Zoology is the science of animals. It embraces 

 every scientific question that may be raised concerning 

 animals — their form, structure, functions, habits, their 

 affinities, their distribution in time geologically and in 

 space geographically. The subject of this course is only 

 a part of zoology. 



The most fundamental divisions of zoology may be 

 clearly brought out by considering an animal in differ- 

 ent ways. We may study the external form of the 

 whole and of each part; then cut into and dissect and 

 determine the form and structure of the internal organs 

 as far as the naked eye can see. Then with the micro- 

 scope we determine the minute structure of every tis- 

 sue and organ. All of this is anatomy, although the 

 naked-eye anatomy is often called morphology, and the 

 minute anatomy histology. All this can best be studied 

 in the dead animal. 



Or, again, we may study the functions of the living 

 animal— i. e., the work that each part or organ performs, 

 and the manner in which they all co-operate for the 

 common life and happiness of the animal. This is 

 called physiology, and can be studied only in the living 

 animal. 



But, again, we may study not only the living mature 

 animal, but the living growing animal. Commencing 

 with the yet, apparently, unorganized egg, we may trace 



