Notes, ii. 2. • 157 



being turned towards the upper part of the universe (ii. 10, 5). The front of man is 

 chosen in preference to the back, for the growth of hair (ii. 14, 3). The nictitating 

 membrane comes from the canthus in front, rather than the canthus on the side (ii. 13, 7). 

 The heart, being the noblest part, is in front and in the upper half of the body (iii. 4, 6), 

 and so on. 



It is almost entirely as a deduction from this mischievous dogma that he infers that the 

 blood of the upper parts and of the right side is hotter than, or in some way or other 

 superior to, that of the lower parts and left side. I say "almost entirely," because even 

 here A. doubtless thought that his a priori statement was confirmed by some actually 

 observed facts. Thus he saw the vena cava and the aorta running side by side down the 

 trunk of the body, both containing blood. The vena cava he noticed was larger than 

 the aorta and lay in its general course on the right of the latter ; he also noticed that 

 the blood in the two differed in aspect (iii. 4, Note 24), as also did that of the right 

 and left ventricles. He supposed that the vena cava nourished the right side of the 

 body, on which it was placed, and the aorta the left side. Hence his statement that the 

 blood of the two sides differed in quantity and quality. He found, again, in some animals 

 the blood of the head of a brighter hue than that of the rest of the body (ii. 7, Note 12). 

 Here was evidence of the superiority of the upper parts to the lower. Another observa- 

 tion can hardly have failed to have been made by him, and to have confirmed his previous 

 opinion. When a limb is much exercised, not only is the general temperature of the 

 body raised, but that of the limb itself rises higher than that of the unused parts. The 

 right arm, being the one used preferentially by most men in any action requiring great 

 muscular force, is often so much hotter than the left that the difference is readily percep- 

 tible to the touch without any instruments. This may easily have led A. to believe that 

 the blood of the right side was hotter than that of the left, as his previous observations 

 bad led him to believe it was more abimdant. Still it is not to be denied, that the 

 statement was in the main a priori ; and that it had, as such dogmas invariably have, 

 the mischievous effect of blinding its acceptor's eyes to facts palpably inconsistent 

 with it. 



7. No greater differences that is than occur within the range of a genus (cf i. i, 

 Note 2). 



8. This was the opinion of Empedocles ; it is discussed at length in De Resp. 14. 

 The coldness of water-animals is at any rate in part due to the rapid loss of heat to 

 which they' are subjected by aquatic life ; and thus their temperature often rises when 

 they are taken out of the water and kept in the air, where the conduction is much less 

 rapid. This was observed by Spallanzani to be the case with many fishes, and more 

 recently by Valentin with Aplysise. 



9. Cf. ii. 7, Note 19. The question whether the catamenia are an . indication of 

 greater heat in the female is discussed in De Gen. iv. i, and answered in the negative. 



10. A. has left special treatises on Sleeping and Waking, Youth and Old Age, Life and 

 Death ; but the treatise on Health and Disease, if ever written, is lost. His general 

 views however, as may be gathered from the first section of the Problemata, were as 

 follows. The characteristics of a living body are that it is hot and contains fluid* matter ; 

 of the dead body that it is cold and without fluid. The coldness is perceptible to 

 the touch, and the want of fluid to the eye; for not only do the fluids coagulate, 

 but the whole body turns to dust. The heat and moisture of the body are at their 

 maximum in youth. For there is a constant exhalation of fluid and heat going on 

 during life, so that the body gradually becomes colder and its fluid less abundant. The 

 older therefore the body, the more easily is its heat extinguished by any chance cause 



