CORRELATION 11 



development of the teeth (as in Ruminants) is accounted for 

 by saying that the animal needs its complex stomach 

 to make up for the shortcomings of its teeth ! (De Partibns, 

 iii., 14, 674 b .) Other examples of correlation were not 

 susceptible of this explanation in terms of final causes. He 

 lays stress on the fact, in the main true, of the inverse 

 development of horns and front teeth in the upper jaw, 

 exemplified in Ruminants. He explains the fact in this way. 

 Teeth and horns are formed from earthy matter in the body and 

 there is not enough to form both teeth and horns, so " Nature 

 by subtracting from the teeth adds to the horns ; the 

 nutriment which in most animals goes to the former being 

 here spent on the augmentation of the latter" (De Partibns, 

 iii., 2, 664 a , trans. Ogle). A similar kind of explanation is 

 offered of the fact that Selachia have cartilage instead of 

 bone, "in these Selathia Nature has used all the earthy 

 matter on the skin [i.e., on the placoid scales] ; and she 

 is unable to allot to many different parts one and the same 

 superfluity of material " (De Partibus, ii., 9, 655*, trans. Ogle). 

 Speaking generally, " Nature invariably gives to one part 

 what she subtracts from another " (loc. cit., ii., 14, 658 a ). 



This thought reappears again in the ipth century in 

 E. Geoffroy St Hilaire's lot de balancement and also in 

 Goethe's writings on morphology. For Aristotle it meant 

 that Nature was limited by the nature of her means, that 

 finality was limited by necessity. Thus in the larger animals 

 there is an excess of earthy matter, as a necessary result of 

 the material nature of the animal ; this excess is turned by 

 Nature to good account, but there is not enough to serve both 

 for teeth and for horns (loc. cit., iii., 2, 663 b ). 



But there are other instances of correlation which seem to 

 have taxed even Aristotle's ingenuity beyond its powers. 

 Thus he knew that all animals (meaning viviparous 

 quadrupeds) with no front teeth in the upper jaw have 

 cotyledons on their foetal membranes, and that most animals 

 which have front teeth in both jaws and no horns have no 

 cotyledons (De Generatione, ii., 7). He offers no explanation 

 of this, but accepts it as a fact. 



We may conveniently refer here to one or two other ideas 

 of Aristotle regarding the causes of form. He makes the 



