in the Jiccu/istruction uf extinct I'^crtebrate Forms. 471) 



by their reciprocal reaction to the same definitive end. None of 

 these parts can be changed without aft'ecting the others ; and 

 consequently each taken separately indicates and gives all the 

 rest/ 



" After this, Cuvier gives his well-known examples of the 

 correlation of the parts of a Carnivore, too h)iig for extract, and 

 of which therefore his summation merely will be given : — 



" ' In a word, the form of the tooth involves that of the con- 

 dyle ; that of the shoulder-blade ; that of the claws : just as the 

 equation of a curve involves all its properties. And just as by 

 taking each jjroperty separately, and making it the base of a 

 separate equation, we should obtain both the ordinary equation 

 and all other properties whatsoever which it possesses ; so, in 

 the same way, the claw, the scapula, the condyle, the femur, and 

 all the other bones taken separately, will give the tooth, or 

 one another ; and by commencing with any one, he who had a 

 rational conception of the laws of the organic (Economy, could 

 reconstruct the whole animal.' 



" Thus far Cuvier; and thus far, and no further, it seems that 

 the compilers, and eo])iers, and popularizers, and id genus omne, 

 proceed in the study of him. And so it is handed down from 

 book to book, that all Cuvier's restorations of extinct animals 

 were effected by means of the principle of the physiological 

 correlation of organs. 



" Now let us examine this principle ; taking, in the first place, 

 one of Cuvier's own arguments and analysing it ; and in the 

 second place, bringing other considerations to bear. 



" Cuvier says — ' It is readily intelligible that Ungulate animals 

 must all be herbivorous, since they possess no means of seizing 

 a prey (1). We see very easily also, that the only use of their 

 fore-feet being to support their bodies, they have no need of so 

 strongly formed a shoulder ; whence follows the absence of 

 clavicles (2) and acromion, and the narrowness of the scapula. 

 No longer having any need to turn their fore-arm, the radius 

 will be united with the ulna, or at least articulated by a gingly- 

 mus and not arthrodially with the humerus (3). Their herbi- 

 vorous diet will require teeth with flat crowns to bruise up 

 the grain and herbage ; these crowns must needs be unequal, 

 and to this end enamel must alternate with bony matter (4) : 

 such a kind of crown requiring horizontal movements for tritu- 

 ration, the condyle of the jaw must not form so close a hinge as 

 in the Cai-nivora ; it must be flattened ; and this entails a cor- 

 respondnigly flattened temporal facet. The temporal fossa which 

 will have to receive only a small temporal muscle will be shallow 

 and narrow (5).' 



The various propositions are here marked with numbers, to 



uri 



