PRINCIPLE OF CONNECTIONS 53 



Vertebrates, with the homologies 'of the bones of the sternum, 

 and with the determination of the pieces of the skull, 

 particularly in the crocodile. All Geoffroy's morphological 

 doctrine is found in them, but for the full expression of his 

 views we must take his chief work, the Philosophie anatoinique, 

 particularly the first volume (iSiS). This volume contains, 

 beside the important " Discours preliminaire" and " Introduc- 

 tion " which we shall presently consider in detail, five 

 memoirs, which deal with the various bones connected with 

 the respiratory organs in fishes (the bones of the operculum, 

 of the hyoid, of the branchial arches, of the pectoral girdle), 

 and seek to discover their homologies with corresponding 

 bones in air-breathing Vertebrates. 



" Can the organisation of vertebrated animals be referred 

 to one uniform type?" This is the question with which the 

 Philosophic atiatouiiqne opens, the question to which the 

 whole book is an answer. But is it not generally acknowledged 

 by naturalists that Vertebrates are built upon one uniform 

 plan, that, for instance, the fore limb may be modified for 

 running, climbing, swimming, or flying, yet the arrangement 

 of the bones remain the same? How else could there be a 

 " natural method " of classification ? 1 



But the homologies so drawn repose upon a vague and 

 confused feeling for likenesses ; they are not based upon an 

 explicit principle. What general principle can be applied ? 

 " Now it is evident that the sole general principle one can 

 apply is given by the position, the relations, and the 

 dependencies of the parts, that is to say, by what I name 

 and include under the term of connections!' For instance, 

 the part known as the hand in man and generally as the 

 fore foot in other Vertebrates, is the fourth part in order 

 in the anterior member, and its homologue can always 

 be recognised by this fact of its connections (p. xxvi.). The 

 principle of connections serves as a guide in tracing an 

 organ through all its functional transformations, for " an 

 organ can be deteriorated, atrophied, annihilated, but not 

 transposed " (p. xxx.). 



It is this principle which enables one to follow out in 

 detail the further fundamental conception that in every 

 1 Discours preliminaire, pp. xv.-xxiv. 



