434 NINETEENTH CENTURY* 



which the food is to pass. But Cuvier proved that this is 

 true not only of the teeth but of every bone in the skeleton 

 of an animal. 



'Every organised being,' he says, 'forms a whole and 

 entire system . . . none of its parts can change without a 

 change of the others also. Thus, if the stomach of an 

 animal is made so as only to digest fresh flesh, his jaws 

 must be formed to devour the prey, his claws to seize and 

 tear it, his teeth to divide the flesh, and the whole system of 

 his organs of motion to follow and overtake it. Nature 

 must even have planted in his brain the necessary instinct to 

 hide himself and lay snares for his victim. These are the 

 general conditions of a carnivorous life, and all animals who 

 are to live this life must fulfil them, otherwise they cannot 

 exist. And besides these general conditions there are 

 special ones, according to the particular kind of life the 

 animal has to live, and each of these require modifications 

 in the form of the organs ; so that not only the class, but the 

 order, the genus, and even the species of an animal are 

 revealed by each part of it.' 



And now you will understand why Cuvier could not 

 believe St.-Hilaire's theory that all the parts of one class of 

 animals such as the vertebrate animals, for example are 

 made on one model, and that when some organ has to play 

 a different part it is altered, and not created for the purpose. 

 Cuvier was strongly impressed with the beautiful agreement 

 in every part of each particular animal, which enables it to 

 provide for all its wants ; while St.-Hilaire was equally im- 

 pressed with the general agreement between the structure of 

 all animals in any one great class. Both these views were 

 true, but in the state of knowledge at u,at time it was very 

 difficult to reconcile them. You must bear this in mind, 

 because it is one of the difficulties upon which light is thrown 



