142 HISTOEY OF THE WORKS OF CUVIER. 



longer changed, for species is a tiling fixed and changes not ; btit the name of 

 the genus might change, for the genus only denotes relations, and relations may 

 vary in proportion as the number of species varies. These simple ideas had, 

 till then, not been comprehended. 



But Linnaeus, who rendered these two great services, is perhaps, of all nat- 

 uralists, he who most contributed to the prevalence, at least lor a certain time, 

 of the use of artificial methods. Now, an artificial method gives only the name 

 of species ; the natural method alone gives the name and the relations of species. 

 An artificial method may conduct to names, even while placing in approxima- 

 tion objects the most dissimilar, and for the very reason that it gives only the 

 name of objects. Thus the connections not being consecutive, the artificial 

 method is not of a logical order. That method is alone logical in which species 

 the most similar are placed beside one another, and species the most unlike are 

 furthest removed from one another. Each group therein has the greatest possible 

 number of common properties. And if the groups are contained one in another, 

 if we ascend from one to others by a series of propositions more and more gen- 

 eral, we possess the science entire. But what are the means for arriving at this 

 logical or natural method ? These means are of two orders : rational or empirical. 



An organized being is a whole ; its different parts, therefore, have necessary 

 relations to one another. Now, the more important any part, that is to sa^^, the 

 more essential by the order of its functions, the more do its modifications involve 

 corresponding ones in all the rest. Everything, therefore, consists in knowing 

 the relative importance of the parts, and in subordinating one to the other in the 

 method, as they are sul)ordinated in the organization itself. In this resides the 

 whole rational principle of method. Thus, the nervous centres, the brain, the 

 spinal marrow, by which the animal is essentially what it is, give the first groups 

 of the method ; the respiratory and circulatorii centres, the lungs, the heart, by 

 means of which it partakes of its present life, give the second ; the digestive cen- 

 tres, by which it sustains that life, give the third, and so on in succession. 



The naturalists have onl}^ succeeded by long tentatives in conducting the dis- 

 tribution of animals to the point of perfection which it has reached _: they have 

 arrived at that point a posteriori ; they might have arrived at it a priori, by 

 the direct determination* of the relative importance of the organs. Now, so far 

 as the relative importance of the organs is known, we have a rational method ; a 

 method a priori. When the relative importance of the organs is not known, we 

 are guided by their constancy ; we have then only a method a posteriori, an em- 

 pirical method. The most constant organ is regarded as the most important ; 

 the constancy of a relation, taken as a fact, supplies the reason of that relation, 

 until that reason is known. 



Thus, for example, all ruminating animals have the foot cloven ; all animals 

 which have horns, ruminate, &c. These are constant relations, but what is the 

 reason of this constancy ? We know it not. And j'et, since these relations are 

 constant, we may employ them, with confidence, in our methods. Again, insects 

 which breathe by means of trachea, are deficient in conglomerate and compact 

 glands. Their secretory organs are only canals or simple tubes. We know at 

 present the reason of this fact. It is because animals which respire by trachea 

 have no circulation, and there needs a circulation to make the blood penetrate 

 into conglomerate and compact glands. But before the reason of the fact was 

 known, the fact itself was known ; it was shown to be constant ; and from the 

 very circumstance of its being constant, it might thenceforth be employed in 

 method. Constancy, therefore, represents importance. 



Thus, there are two kinds of method, or, to speak with more exactness, there 



* Direct detennination,wh\ch is only obtained through physiology. And herein, as has been 

 ah'eady said, is the true secret of the great results obtained by M. Cuvier. It was because 

 his vast genius embraced all— anatomy, physiology, zoology ; and made each of those sciences 

 co-operate in turn to the progress of the others. 



