DOCTRINE OJ? FINAL CAUSES. 51 



a definite and regular manner, be adjusted and subordinated to one 

 another. This relation of dependence, necessarily resulting from the 

 conception of the organism, has been very suitably termed " Corre- 

 lation " of organs ; and many years ago served for the establishment 

 of several principles, the cautious application of which has been of 

 great service to the comparative method. 



Each organ, in order that it may properly discharge the functions 

 which are requisite for the maintenance of the entire machine, must 

 comprise a certain number of working units, and consequently must 

 have a certain size and possess a form dependent partly on its func- 

 tions and partly on its relation with other organs. If an organ 

 becomes abnormally enlarged it increases at the expense of the sur- 

 rounding organs, and the form, size, and function of the latter 

 become injuriously modified. Fromthis isdeducedthe principle to which 

 Geoffrey St. Hiliare gave the name if he was not the first to recognise 

 it of the "principe du balancement des organes," and this enabled that 

 investigator to establish the doctrine of " Abnormalites " (Teratology). 



The organs which are physiologically similar, i.e., organs which per- 

 form in general the same function, as, for instance, the teeth or the 

 alimentary canal or the organs of movement, undergo great and 

 various modifications ; and the particular methods of nutrition and 

 habits of life, as well as the external conditions which must be ful- 

 filled if the life of any particular genus is to continue, depend upon 

 the special arrangement and action of the individual organs. Given 

 therefore the special form and arrangement of a particular organ or 

 part of an organ, it is possible to arrive at conclusions concerning 

 the special structure, not only of many other organs, but even of 

 the entire organism, and to reconstruct to a certain extent the whole 

 animal so far as its essential features are concerned. This was first 

 done by Cuvier for many extinct Mammalia, with the aid of scanty 

 fragments of fossil bones and teeth, in a masterly manner. 



If we regard the life of the animal and its maintenance, not as the 

 result, but as the end sought, as the aim of all the special arrange- 

 ments and actions of the individual organs and parts, we are led to 

 the " principe des causes finales" (des conditions d' existence) of Cuvier, 

 and consequently to the so-called teleological doctrine by which we 

 certainly do not attain to a mechanico-physical explanation. However 

 that may be, this theory, if it be regarded merely as an expression 

 of the reciprocal relations which necessarily exist between the form 

 and function of the parts and of the whole, and not in the Cuvierian 

 sense as implying the existence of design, renders important and 



