In this bird the reverse takes place of what was mentioned to happen in the cassowary and American ostrich, for the stones and other hard bodies swallowed by these birds, must, from their weight, force a way into the gizzard, which is a large cavity adapted to receive them; but here all such substances must remain in the cardiac cavity, both from its being the most depending part, and from the cavity of the gizzård being too small to admit of their entering it.

The cardiac cavity contained stones of various sizes, pieces of iron, and halfpence; but between the grinding surfaces of the gizzard, there were only broken glass beads of different colours, and hard gravel mixed with the food.

In taking a review of the structure of the digestive organs of the cassowary, the American, and African ostrich, whose mode of progressive motion is the same, we find their organs very differently circumstanced with respect to the means of œconomising their food.

The cassowary and American ostrich differ from birds that fly, in having the solvent glands placed in a cavity of unusual size and the muscular structure of the gizzard uncommonly weak; the mode of progressive motion, which is a kind of run, producing so much agitation between the stones and the food, as to render a stronger muscular action unnecessary.

In the cassowary there appear to be no considerations of œconomy in the management of the food in the process of digestion, the solvent glands are less complex than in the ostrich, as is avowed by those who have examined them,* the food has a free passage from the gizzard into the intestines, which are unusually wide and short, so that its passage • Vide PERRAULT's Comp. Anat. 1676.

through them is very rapid, and is rendered still more so by the stones of a large size employed in the gizzard passing out at the anus. This I learnt from Sir JOSEPH BANKS, who was present at the Cape of Good Hope when one of these birds, to his great astonishment, voided nearly half a bucket full of

stones.

In the American ostrich there will be less waste of the food than in the cassowary, as the solvent glands are of a more complex structure, as there is a less ready outlet from the gizzard, and as the intestines are longer and have a variety of convolutions.

In the African ostrich the means of oeconomising the food are greater than in other birds; the glands have the same structure as in the American species, are more numerous, are spread over a larger surface, there is a more extensive cavity in which the substances it feeds upon are triturated; and beyond this, a grooved gizzard for the more accurate breaking down of the food. The intestines also are longer and more varied in their course.

All these provisions of nature fit this bird to live in the sandy deserts, of which it is the natural inhabitant; and are not bestowed upon the others that live in countries where food is more abundant.

It is a curious circumstance that the situation of the solvent glands, the shape of the cardiac cavity and position of the gizzard in the alca alle among carnivorous birds is nearly the same as that of the African ostrich among birds that live principally on vegetable food.

EXPLANATION OF THE plates.

PLATE XI.

The gizzard of the Soland goose laid open to show the situation and appearance of the solvent glands. The engraving is of the natural size.

PLATE XII.

Shows the form and internal structure of the cardiac cavity and gizzard in the wood-pecker, the sea-gull, and the little auk, all of the natural size.

Fig. 1. The external appearance of the cardiac cavity and gizzard in the wood-pecker.

9. The internal appearance of the cardiac cavity and gizzard of the wood-pecker.

3. The internal appearance of the cardiac cavity and the cavity of the gizzard in the sea-gull.

4. The internal appearance of the cardiac cavity and gizzard of the little auk.

PLATE XIII.

Two views of the digestive organs of the parrot of the natural size.

Fig. 1. An external view of the crop, cardiac cavity, and gizzard.

2. An internal view of the same parts.

PLATE XIV.

An external view of the cardiac cavity and gizzard of the American ostrich, one-fourth of the natural size.