136 HISTORICAL EEVIEW. 



vestigations in numerous works, especially in his " Lemons d'Anatomia 

 comparee " (1805). 



In his celebrated treatise* published in 1812, on the arrangement 

 of animals according to their organization, he established a new 

 and essentially changed classification, which was the first serious 

 attempt to build up a natural system. Cuvier did not, as most 

 zootomists had done, look upon anatomical discoveries and facts as 

 in themselves the aim of his researches, but he contemplated them 

 from a comparative point of view, which led him to the establishment 

 of general principles. By considering the peculiarities in the ar- 

 rangements of the organs in relation with the life and unity of the 

 organism, he recognised the reciprocal dependence of the individual 

 organs, and appreciating fully the idea of the " correlation " of parts 

 already discussed by Aristotle, he developed his principle of the con- 

 ditions of existence without which an animal cannot live (principe 

 des conditions d 'existence ou causes finales}. " The organism con- 

 sists of a single and complete whole, in which single parts cannot be 

 changed without causing changes in all the other parts." By com- 

 paring the organizations of many different animals, he found that the 

 important organs are the most constant, and that the less important 

 vary most in their form and development, and even are not univer- 

 sally present. 



He was thus led to the principle so important for the systematist 

 of the subordination of characters (princi})e de la subordination des 

 caracteres). Without being ruled by the pre-conceived idea of the 

 unity of all animal organization, he became convinced, from a conside- 

 ration of the differences in the nervous system and in the arrangement 

 of the more important systems of organs, that there were in the 

 animal kingdom four main types (enibranchements), " general plans 

 of structure on which the respective animals appear to be modelled, 

 and whose individual subdivisions, as they may be called, are only 

 slight modifications based on the development or the addition of 

 some parts, without the plan of the organization being thereby 

 essentially changed." 



These four groups (embranchements Cuvier, Typen Blainville) 

 were the Yertebrata, Mollusca, Articulata, and Radiata. 



The views of Cuvier, who in knowledge of anatomical and zoologi- 

 cal detail stood far above all his contemporaries, were, however, in 

 opposition to the theories of men of note (the so-called School of 



* " Sur un nouveau rapprochement a etablir entre les classes qui composent le 

 regne animal." Ann. des Museum (VH'ist. Nat., Tom XIX., 1812. 



