THE STUDY OF AN ANIMAL TYPE 



In the study here outlined it is assumeti that the objective is 

 that of gaining a better understanding of the biological nature 

 of the high(>r animals and man. At the outset of such a study it 

 is necessary that one should acquire a clear conception of what 

 is signified by the term "living individual" or "organism" as a 

 center about which to organize zoological kncjwlcdge. An 

 organism is something more than a mere spatial association of 

 structural components, however orderly they may be arranged. 

 What constitutes the body of the animal? How are the struc- 

 tural components of the body related? What are the services 

 of the various parts and why are these services necessary? How 

 are these diverse structures and their activities maintained and 

 combined to form a unit and what is that unit? Studies along 

 the lines suggested by such questions provide the basis for a 

 comprehension of what is meant by the term "organism." These 

 deliberations are, therefore, begun with the study of an animal 

 type which will furnish the foundation upon which to place a 

 conception of an organism. The frog is chosen as a convenient 

 form, since it is a familiar animal exhibiting a moderately complex 

 structure and in all fundamental respects of structure and phys- 

 iology may be compared directly with man. The structural 

 similarity is easily recognized by standing the frog upon its 

 hind legs and making the comparison part for part. 



In the frog and other complex animals it is possible to dis- 

 tinguish general regions of the body and directions within the 

 body without reference to the movements of the animal or to any 

 part of the environment. When such a state prevails the 

 method of naming part? and directions is known as iiitrinsic 

 io-ponomy. The following is a list of terms which will bo employed 

 according to this method of naming parts: 



Dorsum, or back, that side of a orawlinR or (luadrupodal animal norinally 

 away from the sulistratum (support) upon which it rests. 

 Dorsad, toward the l)a<'k or in that direct i<m. 

 Dorsal, |)ertaiiiinK to the hack. 



Venter, or heily, that side of the animal normally ti»ward tlu' substratum. 

 Ventrad, toward the venter or in a ventral direction. 



