GREEK BIOLOGY AND MEDICINE 



known to him for the most part — but not 

 altogether, since now and then the modern 

 investigator " discovers " what Aristotle knew. 

 Yet whole provinces of the considerations of 

 modern biology scarcely touched him. All the 

 more marvellous were the forward thrusts of 

 his mind toward what the distant future should 

 make clear. One of those thrustings forward 

 was the classification of animals, which may 

 be drawn from his writings. 



His fundamental division was into animals 

 with blood and animals without, that is to say, 

 those who have no true blood but a different 

 fluid performing a like nutritive function. 

 This division coincides with the modern one 

 into vertebrates and invertebrates, ascribed to 

 Lamarck (i 744-1 829). Through the constit- 

 uent groups under both divisions will be found 

 a series of gradations in foetal development 

 within the parent's body; and these determine 

 the Aristotelian group formation. 



Man, the Cetacea, viviparous quadrupeds, 

 birds, reptiles, fishes, bony and then cartilag- 

 inous, come within the division of animals 

 with blood. Aristotle had no conception of the 

 mammalian ovum, and consequently regarded 

 the embryo of mammals as born alive within 



[54] 



