had often of
necessity to be founded on a very slight basis of facts. Yet,
notwithstanding this drawback, so great was the sagacity of this
philosopher, that many of his generalizations, which he himself probably
looked upon as temporary, have held their ground for twenty centuries,
or, having been lost sight of, have been discovered and put forward as
original by modern biologists. Thus "the advantage of physiological
division of labour was first set forth," says Milne-Edwards, "by myself
in 1827;" and yet Aristotle had said[13] that "whenever Nature is able
to provide two separate instruments for two separate uses, without the
one hampering the other, she does so, instead of acting like a
coppersmith, who for cheapness makes a spit-and-a-candlestick in
one.[14] It is only when this is impossible that she uses one organ for
several functions."

In conclusion, we may say that the great Stagirite expounded the true
principles of science, and that when he failed his failure was caused by
lack of materials. His desire for completeness, perhaps, tempted him at
times to fill in gaps with such makeshifts as came to his hand; but no
one knew better than he did that "theories must be abandoned unless
their teachings tally with the indisputable results of observation."[15]

FOOTNOTES:

[3] Pliny, "Natural History," viii. c. 16.

[4] "History of Animals," i. 11.

[5] Bk. iii. 19.

[6] "Meteorology," iv. 7-11.

[7] "History of Animals," i. 16.

[8] "History of Animals," vi. 3.

[9] "On some of the errors attributed to Aristotle."

[10] "History of Animals," i. 17.

[11] See Professor Huxley's article already referred to.

[12] "Aristotle," by G. H. Lewes, p. 325.

[13] "De Part. Anim.," iv. 6.

[14] {obeliskolychnion}.

[15] "De Gener.," iii. 10, quoted by Dr. Ogle.

GALEN.

_GALEN._

Under the Ptolemies a powerful stimulus was given to biological studies
at Alexandria. Scientific knowledge was carried a step or two beyond the
limit reached by Aristotle. Thus Erasistratus and Herophilus thoroughly
investigated the structure and functions of the valves of the heart, and
were the first to recognize the nerves as organs of sensation. But,
unfortunately, no complete record of the interesting work carried on by
these men has come down to our times. The first writer after Aristotle
whose works arrest attention is Caius Plinius Secundus, whose so-called
"Natural History," in thirty-seven volumes,