474 SCIENCE PROGRESS 



comparison any distinctive characters which the animals might 

 present, regardless whether they dealt with differences of 

 structure or of function. This comparative work afforded the 

 material with which subsequent workers began to build up a 

 classification of the animal kingdom. Accordingly we find the 

 early classifiers using indifferently likeness of function and of 

 structure. So, for example, Vicq d'Azyr, who was Professor 

 of Anatomy in Paris from 1774 to 1794, takes as a ground for 

 classification not only structural similarities between animals, 

 but also the presence in them of organs, such as those of respira- 

 tion, whose likeness is purely one of function. 



This method survived well into the beginning of the nine- 

 teenth century. Duges, a prominent member of the French 

 school who wrote about 1830, speaks of the species as "un type 

 ideal de forme, d'organisation, de mceurs." In much the same 

 way Cuvier's classification of the animal kingdom was partly 

 morphological and partly physiological. He took as character- 

 istics certain organs which are distinguished from others, not 

 by their structure or anatomical relations, but by their functions 

 only. He even went so far as to lay particular stress upon a 

 structure as a ground for classification, if its function was 

 of more than ordinary importance. This attitude is well 

 expressed in his own words : " toutes les parties, toutes les 

 formes, toutes les qualites d'un organe ne sont pas egalement 

 propres a fournir des caracteres pour les classes superieures ; 

 ce sont seulement celles de ces formes et de ces qualites qui 

 modifient d'une maniere importante la fonction a laquelle cet 

 organe est affecte." 



Now, in so far as Cuvier or any other zoologist used the 

 characters of animals simply and directly as a test of their 

 likeness, and consequently of the propriety of their being 

 classed together, it could be of no importance whether the 

 characters used were matters of function or of structure — one 

 point of likeness will serve as well as another to mark the 

 similarity. But to this direct method there soon succeeded 

 one which depended upon the philosophical doctrine of the 

 common plan of organisation of animals. This idea was 

 . strongly developed at the beginning of the nineteenth century 

 by Oken and Goethe, with other members of the imaginative 

 German School of " Naturphilosophie," and gained a great 

 hold over the biologists of the time. As a corollary of the 



