24 THE HISTORY OF SCIENCE 



fested his characteristic inclination to be at once ab- 

 stract and concrete. His works display a knowledge 

 of over five hundred living forms. He dissected speci- 

 mens of fifty different species of animals. One might 

 mention especially his minnte knowledge of the sea- 

 urchin, of the rnurex (source of the famous Tyrian 

 dye), of the chameleon, of the habits of the torpedo, 

 the so-called fishing-frog, and nest-making fishes, as 

 well as of the manner of reproduction of whales and 

 certain species of sharks. One of his chief contribu- 

 tions to anatomy is the description of the heart and 

 of the arrangement of the blood-vessels. A repug- 

 nance to the dissection of the human body seems to 

 have checked to some extent his curiosity in refer- 

 ence to the anatomy of man, but he was acquainted 

 with the structure of the internal ear, the passage 

 leading from the pharynx to the middle ear, and the 

 two outer membranes of the brain of man. Aristotle's 

 genius did not permit him to get lost in the mere de- 

 tails of observed phenomena. He recognized resem- 

 blances and differences between the various species, 

 classified animals as belonging to two large groups, 

 distinguished whales and dolphins from fishes, recog- 

 nized the family likeness of the domestic pigeon, the 

 wood pigeon, the rock pigeon, and the turtle dove. 

 He laid down the characteristics of the class of in- 

 vertebrates to which octopus and sepia belong. Man 

 takes a place in Aristotle's system of nature as a 

 social animal, the highest type of the whole series of 

 living beings, characterized by certain powers of re- 

 call, reason, deliberation. Of course it was not to be 

 expected that Aristotle should work out a fully sat- 

 isfactory classification of all the varieties of plants 



