4. Young animals excrete more carbonic acid than old ones; this is most marked in amphibia. For example 100 grams of an old frog (Rana temporaria) exhaled in six hours ·213 grm., whereas 100 grams of a young frog gave off in the same time ·765 grm.
5. The larvæ of insects exhale less carbonic acid than the insects themselves.
6. Different individuals of the same species exhale in the same time nearly the same quantity of carbonic acid in proportion to their body-weight.
In the second part of this paper the author
describes experiments in the influence of coloured light on the excretion of carbonic acid; in the same animal (mouse) and for the same time.
He concludes that—
1. The excretion of carbonic acid is less in ordinary daylight than in coloured light.
2. The violet and red rays exercise the least influence on the excretion of carbonic acid, the green and yellow are the most active; and the milk-white and blue rays occupy an intermediate position. The relation of these different actions may be expressed by the following figures:—
| Violet. 86·89 | Red. 93·38 | Milk-white. 100 |
| Blue. 122·63 | Green. 128·52 | Yellow. 174·79 |
Finally, the author experimented with a mouse during the night, and found then the excretion of carbonic acid at that time is considerably less than during the day.