ORDER CARNASSIER. 423 



circular. It is also capable of much alteration, not only in 

 size, but also in figure, resulting from the degree of light 

 acting upon it, and occasionally from some sudden mental 

 impulse, so as to be sometimes round, sometimes oval, and 

 sometimes a mere vertical line in the same animal. 



There are some positions so universally considered as 

 true, that no one ever thinks of doubting them ; and it is, 

 indeed, on such, that all reasoning must be grounded : but 

 we cannot be over scrupulous in admitting, or too nice in 

 investigating any proposition, before it is classed with those 

 fundamental axioms as self-evident, and therefore not re- 

 quiring to be demonstrated. 



That the pupils of Cats are oval, and that therefore they 

 are enabled to see in the dark, is an assertion very generally 

 made, and seldom questioned ; and some naturalists, ob- 

 serving that the felinae vary in this particular among them- 

 selves, have separated them into diurnal and nocturnal 

 species ; distinguishing the former by the circular pupil, 

 and the latter by that of an oval figure. It may, neverthe- 

 less, be doubted, whether the shape of the eye-pupil be at 

 all connected with the extent of the power of vision : the 

 size of it must, in all probability, be materially so ; but it 

 does not appear certain, that those animals which dilate 

 the iris, so as to elongate the pupil, have also the greatest 

 power of contracting the former, and consequently of en- 

 larging the latter, more than others which have the pupil 

 at all times circular. 



Major Smith has observed, on this subject, that the disk- 

 ous or circular eye-pupil is believed to be diurnal, and the 

 Lion and Tiger are both, in general, associated together on 

 this account ; but the Lion, although he sees by day, may 

 be said, probably, never to hunt his prey while the sun is 

 above the horizon, unless pressed in an extraordinary de- 

 gree. The pupil of his eye is also at all times circular, and 

 always of a yellowish colour. The Tiger, on the contrary, 



