A HISTORY OF SCIENCE 



tiquity. They show us that Aristotle had gained 

 possession of the widest range of facts regarding the 

 animal kingdom, and, what is far more important, had 

 attempted to classify these facts. In so doing he be- 

 came the founder of systematic zoology. Aristotle's 

 classification of the animal kingdom was known and 

 studied throughout the Middle Ages, and, in fact, re- 

 mained in vogue until superseded by that of Cuvier in 

 the nineteenth century. It is not to be supposed that 

 all the terms of Aristotle's classification originated 

 with him. Some of the divisions are too patent to 

 have escaped the observation of his predecessors. 

 Thus, for example, the distinction between birds and 

 fishes as separate classes of animals is so obvious that 

 it must appeal to a child or to a savage. But the ef- 

 forts of Aristotle extended, as we shall see, to less 

 patent generalizations. At the very outset, his grand 

 division of the animal kingdom into blood -bearing and 

 bloodless animals implies a very broad and philo- 

 sophical conception of the entire animal kingdom. 

 The modern physiologist does not accept the classifica- 

 tion, inasmuch as it is now known that colorless fluids 

 perform the functions of blood for all the lower organ- 

 isms. But the fact remains that Aristotle's grand 

 divisions correspond to the grand divisions of the 

 Lamarckian system vertebrates and invertebrates 

 which every one now accepts. Aristotle, as we have 

 said, based his classification upon observation of the 

 blood ; Lamarck was guided by a study of the skeleton. 

 The fact that such diverse points of view could direct 

 the observer towards the same result gives, infer- 

 entially, a suggestive lesson in what the modern 



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