APPENDIX B 



Air is thus set in movement as one continuous entity 

 and is prevented from being dissipated. (This require- 

 ment necessitates that the object struck should have a 

 smooth surface, otherwise the Air cannot be moved as a 

 unity.) Hence here too the medium must be continuous 

 between the sounding object and the sense-organ ; and 

 its movement in turn sets in movement the Air in the 

 ear {De anima II. 420). 



B 



(28) Since {De sensu 438 b 7) there must be light within the Vision. 

 eye as well as in the external medium, the ej-e also will 

 have to be transparent ; hence the eye, or rather that 



part of the e3-e which sees, viz., the ko'^ or pupil, is made 

 of Water {H.A. I. 491 b 20, De sensu 438 a 13 ff., P. A. 

 • II. 656 h 1, O.A. V. 779 b 23 if.). Thus the external 

 medium and the internal constituent are both trans- 

 parent. The substance used for the eye is Water and 

 not Air because ^^'ater is more easily kept in a confined 

 space than Air {De sensu 438 a 15 ; P. A. II. 656 b 2). 

 And it is of course the movement of this part qua trans- 

 parent, not qua fluid, that constitutes sight {G.A. V. 

 780 a 4 ; cf. De sensu 438 a 13 ff.). If the fluid in the 

 eye is already in violent movement owing to some 

 earlier stimulus, it cannot respond to a fresh movement 

 from without {O.A. V. 780 a 8 ff. ; <•/. a 23). 



(29) The sense-organ of Hearing is of Air {De anima III. Hearing. 

 425 a 4 ; cf. P. A. II. 656 b 17 ; G.A. V. 781 a 23) ; and 



'the Air in the ear is built into a chamber (eycaTajxroSd- 

 firp-ai) in order to keep it free from disturbance {npos to 

 aKivrjros (Ivai), SO that it may take up the movements 

 conveyed to it from without, ottcjs aKpi^ius aladdvrjToi 

 Ttdaas Toj 8ia<f>opds rrj^ Kiirqaecus {De anima II. 420 a 10; 

 cf. the very similar phrase frequently used in G.A. V. 

 T79 b — 781 b). This Air in the ear is also described as 

 " connate " (ov/xi^utj? ; De anima II. 420 a 12) ; and it is 

 this Air with which we hear. It is itself always in 

 movement with a proper movement of its own (oiVeia 

 Kimqais) ; sound, however, is of course not this proper 

 movement, but a movement derived from something 

 else {dXXoTpios). 



591 



