corresponds with the nozzle and air valve both, of our bellows. But the
glottis is always opened when the chest is dilated at each inspiration.
How then can the air in any air-cell be kept at a higher tension than
the surrounding atmosphere?

Hunter experimented on the uses of the air sacs, I know, but I have not
his work at hand. It may be that opening one of the air-cells interferes
with flight, but I hold it very difficult to conceive that the
interference can take place in the way you suppose. How on earth is a
lark to sing for ten minutes together if the air-cells are to be kept
distended all the while he is up in the air?

At any rate twenty other illustrations will answer your purpose as well,
so I would not select one which may be assailed by a carping fellow like

Yours very faithfully,

T.H. Huxley.

October 10, 1860.

My dear Spencer [This was written at the time when Mr. Spencer had
issued a notice of discontinuance, and when measures were being taken to
prevent it.],

"A wilful man must have his way," and if you won't let me contribute
towards the material guarantees for the success of your book, I must be
content to add twelve shillings' worth of moral influence to that I
already meant to exert per annum in its favour.