Insectivorous Plants. Darwin Charles

14

As the opacity and porcelain-like appearance of the glands is probably due to the coagulation of the albumen, I may add, on the authority of Dr. Burdon Sanderson, that albumen coagulates at about 155o, but, in presence of acids, the temperature of coagulation is lower. The leaves of Drosera contain an acid, and perhaps a difference in the amount contained may account for the slight differences in the results above recorded.

It appears that cold-blooded animals are, as might have been expected, far more sensitive to an increase of temperature than is Drosera. Thus, as I hear from Dr. Burdon Sanderson, a frog begins to be distressed in water at a temperature of only 85o Fahr. At 95o the muscles become rigid, and the animal dies in a stiffened condition.

15

Mucus from the air-passages is said in Marshall, 'Outlines of Physiology,' vol. ii. 1867, p. 364, to contain some albumen.

Mller's 'Elements of Physiology,' Eng. Trans. vol. i., p. 514.

16

Watts' 'Dictionary of Chemistry,' vol. iii., p. 568.

'Leons sur la Phys. de la Digestion,' tom. i, p. 379; tom. ii. pp. 154, 166, on legumin.

17

The leaves of young plants, before the heart is formed, such as were used by me, contain 2.1 per cent. of albuminous matter, and the outer leaves of mature plants 1.6 per cent. Watts' 'Dictionary of Chemistry,' vol. i. p. 653.

18

It appears, however, according to Schiff, and contrary to the opinion of some physiologists, that weak hydrochloric dissolves, though slowly, a very minute quantity of coagulated albumen. Schiff, 'Phys. de la Digestion,' tom. ii. 1867, p. 25.

19

In all my numerous experiments on the digestion of cubes of albumen, the angles and edges were invariably first rounded. Now, Schiff states ('Leons phys. de la Digestion,' vol. ii. 1867, page 149) that this is characteristic of the digestion of albumen by the gastric juice of animals. On the other hand, he remarks "les dissolutions, en chimie, ont lieu sur toute la surface des corps en contact avec l'agent dissolvant."

20

Sachs remarks ('Trait de Bot.' 1874, p. 774), that cells which are killed by freezing, by too great heat, or by chemical agents, allow all their colouring matter to escape into the surrounding water.

21

As a control experiment bits of albumen were placed in the same glycerine with hydrochloric acid of the same strength; and the albumen, as might have been expected, was not in the least affected after two days.

22

'Leons phys. de la Digestion,' 1867, tom. ii. pp. 114-126.

23

'Leons phys. de la Digestion,' tom. ii. p. 145.

24

Dr. Lauder Brunton, 'Handbook for the Phys. Laboratory,' 1873, pp. 477, 487; Schiff, 'Leons phys. de la Digestion,' 1867, p. 249.

25

Dr. Lauder Brunton gives in the 'Medical Record,' January 1873, p. 36, an account of Voit's view of the indirect part which gelatine plays in nutrition.

26

'Leons,' &c. tom. ii. page 151.

27

Dr. Lauder Brunton, 'Handbook for Phys. Lab.' p. 529.

28

'Leons' &c. tom. ii. page 153.

29

Mr. A.W. Bennett found the undigested coats of the grains in the intestinal canal of pollen-eating Diptera; see 'Journal of Hort. Soc. of London,' vol. iv. 1874, p. 158.

Watts' 'Dict. of Chemistry,' vol. ii. 1872, p. 873.