Notes, ii. i. ^55 



the medium for sight sound and smell alike, but not in virtue of the same qualities. 

 In sight it is the Transparent (Sm^aye's) which is effectual. In smell it is a nameless 

 something, which like the Transparent is common to both elements. And similarly 

 there is another nameless something in them both which serves as the medium of sound. 

 These nameless qualities were afterwards called the Trans-olent \^[o(j\t.ov) and Trans- 

 sonant (SiTjxe's). Cf Torstrik's notes to De Animd, ii. 7. Of these several hypothetical 

 media, the sole survivor is the luminiferous aether of modem physicists. 



13. "Each sense seems to recognise but one pair of contraries. Vision, for instance, 

 recognizes white and black ; hearing, treble and bass ; taste, bitter and sweet ; (smell ?). 

 But in the tangible object there are many contraries, hot and cold, solid and fluid, hard 

 and soft, and other such oppositions" {D. A. ii. il). This leads A. to enquire whether 

 there may not be several different senses included under touch, and confounded together 

 because they have a common medium, viz. the flesh, which hides from sight their really 

 distinct sense organs, which are placed internally, somewhere in the neighbourhood 

 of the heart. . To this question, however, he gives no decided answer. Many modem 

 physiologists hold, as at least probable, that tactile impressions, impressions of pain, 

 and impressions of • temperature, though usually referred in common to touch, have in 

 reality their own distinct organs, central and peripheral. 



14. And therefore, he intends to imply, the least simple. As to the flesh, cf. ii. 10, 

 Note 10 ; ii. 8, Note 2. 



15. Cf. Dejfu. et Sen. I. 



16. What A. means is this. '* Most organs are constructed out of several homo- 

 geneous parts or tissues ; but some, as the heart, of only one. Yet in such a case the 

 organ may be considered one of the heterogeneous parts, in virtue of its definite shape." 

 Thus a cartilage or a horn is made of one tissue, cartilaginous or homy tissue, and 

 yet is- an organ as much as if it were made of several- tissues, because it has a definite 

 shape and size, which suit it to its function. The difference is the same as between 

 silvef and a half-crown. The latter has a definite size and form, which makes it 

 equivalent to an organ; the former is simply material, into the conception of wljich 

 neither size nor form in any way. enter, and answers to the tissue. The one is 

 tVX'JMa'rfff/nei'oj', the other kcrx'hf'-^T^'f'^ov. 



In short A. divides the parts into three classes, as follows : 

 a. Parts purely homogeneous, i.e. tissues. 

 )8. Parts purely heterogeneous, i.e. compound organs. 



7. Parts homogeneous in substance, but heterogeneous as Tiaving a definite shape, 

 i.e. simple organs. 

 In the last of these classes A. includes the heart, which he erroneously supposes to be 

 made of a single tissue ; and says it is capable of being the sensory centre in virtue of 

 its homogeneous substance, and capable of being the motor centre in virtue of its 

 heterogeneous form. 



17. The heart is excepted, because A. thought that it was formed earlier than the blood, 

 which is true if by blood be meant a red fluid. As to the other viscera, cf. iii. 8, Note 2. 



18. A. often {e.g. iii. 4 ; H. A. iii. 3, 8) contrasts the heart with the other viscera in 

 respect to the relation they severally bear to the vessels. The heart, he says, is like an 

 expanded portion of the vessels, in which the blood is stored as in a reservoir or lake 

 (so Dante, " n^l lago del cor"") ; while in the vessels the blood forms a stream. Moreover 

 in the heart no vessel breaks up into branches," whereas in the other viscera this is 

 invariably the case, the vessel sometimes disappearing in the substance of the viscus, as 

 in the kidney (D. P. iii. 9, 5), at other times, as in the liver, passing through. It would 



