INTRODUCTION. 3 



formerly accessible to all, is not sufficient to render it 

 scientific. It is a fatality rather than a triumph to 

 have undergone such a change. The change is an 

 effect rather than a cause. 



When little or nothing was known it was necessary 

 to begin by examining the phenomena which first 

 met the eyes of the observer, such as the customs of 

 animals and the characters which distinguished them 

 from each other. Their differences and resemblances 

 were studied ; they were formed into groups, classed 

 and arranged in an order recalling as much as 

 possible their natural relations. In classifying it is 

 impossible to consider all the facts or the result 

 would be chaos ; it is necessary to choose the 

 characters and to give preponderance to certain of 

 them. This sorting of characters has been executed 

 with the sagacity of genius by the illustrious natural- 

 ists of the last century and the beginning of the 

 present. But the frames which they have traced are 

 fixed and rigid ; nature with her infinite plasticity 

 escapes from them. We render a great homage to 

 the classifiers when we say that they have confined 

 the facts as closely as it is possible to do. The 

 catalogues which they have prepared are of a utility 

 which is unquestionable, although their rdle is to be 

 useful only ; we cannot pretend to make them the 

 expression, the symbol, the formula in which all 

 natural phenomena are to be enclosed. To confound 

 classification with science is to confound the lever 

 with the effect which we expect from it 



Curiosity, moreover, always impels towards that 

 which is least known. External appearances having 

 been studied, the form and function of internal organs 

 were investigated. Physiology and comparative 



