2 ANATOMY OF THE RABBIT 



based on the recognition of differences, the latter being estimated 

 by various features, such as form, colour, texture, or position. On 

 the other hand, because of the class of structure with which it deals, 

 dissection should also be recognized as a method preliminary to 

 others involving the use of the microscope. Further, the analysis 

 should- be followed at each step by a synthesis in the mind of the 

 student, who must keep before him the unity of the individual 

 organism as a whole. 



THE INTERPRETATION OF STRUCTURE 



Gross structure is, in a sense, only an expression of the finer 

 microscopic structure underlying it. Since this relation is more 

 fully discussed below under the head of "General Anatomy," it 

 need only be mentioned here as an element in the interpretation 

 of structure as viewed from the gross standpoint. All animal 

 structure, however, may be considered from two points of view — 

 physiological and morphological. 



The physiological aspect of structure concerns the functions or 

 activities of the living organism and of its individual parts. The 

 contraction of a skeletal muscle is a change in the axial relations of 

 a mass of living protoplasm, but the form and connections of the 

 muscle are such that the contraction results in movement of one 

 bone upon another. The excretion of urine by the kidneys is the 

 final stage of a process which rids the body of soluble waste nitro- 

 genous materials by discharging them into a system of tubes con- 

 nected with the outside of the body. It is essential to recognize 

 that in these, as in the multitude of analogous cases, structure and 

 function are intimately related and serve to explain each other. 



The morphological aspect of structure concerns various features 

 of form and arrangement which, although they have been developed 

 on a basis of utility, cannot be explained purely on that basis. 

 The factors controlling them lie outside the body of the individual 

 and comprise environmental influences and inherent characteristics 

 of the whole race, the interaction of which only through a long 

 series of gradually changing conditions has directed and determined 

 the evolution of the type to which the individual belongs. As 

 applied, to a particular animal, the morphological method consists 

 in explaining its adult structure by reference either to its embryonic 



