24 11. 2. 



such are suited alike for the development of courage and of 

 wisdom. Accordingly the upper parts are superior in these respects 

 to the lower, the male superior to the female, and the right side 

 to the left.^ As with the blood so also with the other parts, 

 homogeneous and heterogeneous alike. For here also such varia- 

 tions as occur must be held either to be related to the essential 

 constitution and mode of life of the several animals, or, in other 

 cases, to be merely matters of slightly better or slightly worse. 

 Two animals for instance may have eyes. But in one these eyes 

 may be of fluid consistency, while in the other they are hard ; 

 and in one there may be eyelids, in the other no such appendages. 

 In such a case, the fluid consistency and the presence of eyelids, 

 which are intended to add to the accuracy of vision, are differences 

 of degree.' 



As to why all animals must of necessity have blood or some- 

 thing of a similar character, and what the nature of blood may be, 

 these are matters which can only be considered, when we have 

 first discussed hot and cold. For the natural properties of many 

 substances are referable to these two elementary principles ; and 

 it is a matter of frequent dispute what animals or what parts of 

 animals are hot and what cold. For some maintain that water 

 animals are hotter than such as live on land,® asserting that their 

 natural heat counterbalances the coldness of their medium ; and 

 again that bloodless animals are hotter than those with blood, 

 and females than males. Parmenides, for instance, and some others 

 declare that women are hotter than men,^ and that it is the 

 warmth and abundance of their blood which causes their menstrual 

 flow, while Empedocles maintains the opposite opinion. Again, 

 comparing the blood and the bile, some speak of the former as 

 hot and of the latter as cold, while others invert the description. 

 If there be this endless disputing about hot and cold, which of 

 all things that affect our senses are the most distinct, what are 

 we to think as to our other sensory impressions ? 



The explanation of the difficulty appears to be that the term 

 " hotter " is used in several senses ; so that different statements, 

 though in verbal contradiction with each other, may yet all be more 

 or less true. There ought then to be some clear understanding 

 as to the sense in which natural substances are to be termed 

 hot or cold, solid or fluid. For it appears manifest, that these are 

 properties on which even life and death '" are largely dependent, 

 648 b. 



