322 OPERATIONS SUBSIDIARY TO INDUCTION. 



litate the study of a particular phenomenon, are, first, 

 to bring into one class all Kinds of things which 

 exhibit that phenomenon, in whatever variety of forms 

 or degrees; and secondly, to arrange those Kinds in a 

 series according to the degree in which they exhibit 

 it, beginning with those which exhibit most of it, and 

 terminating with those which exhibit least. The 

 principal example, as yet, of such a classification, is 

 afforded by comparative anatomy and physiology, 

 from which, therefore, our illustrations shall be 

 taken. 



2. The object being supposed to be, the inves- 

 tigation of the laws of animal life ; the first step, after 

 forming a distinct conception of the phenomenon itself, 

 is to erect into one great class (that of animals) all 

 the known Kinds of beings where that phenomenon 

 presents itself; in however various combinations with 

 other properties, and in however different degrees. 

 As some of these Kinds manifest the general pheno- 

 menon of animal life in a very high degree, and 

 others in an insignificant degree, barely sufficient for 

 recognition ; we must, in the next place, arrange the 

 various Kinds in a series, following one another 

 according to the degrees in which they severally 

 exhibit the phenomenon ; beginning, therefore, with 

 man, and ending with the most imperfect kinds of 

 zoophytes. 



This is merely saying that we should put the in- 

 stances, from which the law is to be inductively col- 

 lected, into the order which is implied in one of the 

 four Methods of Experimental Inquiry discussed in 

 the preceding Book ; the fourth Method, that of Con- 

 comitant Variations. As we formerly remarked, this 

 is often the only method to which recourse can be 



