I have observed that the natives mix the gum of certain trees with the bark, and masticate both together. This is attributed to the difficulty of masticating the gum alone; but I am persuaded that it has another cause also, and that it arises from that experience of the necessity of an additional stimulus to the digestive organ which has taught the Esquimaux and Ottomacs to add sawdust or clay to their train-oil. It arises from the fact that (paradoxical as it may appear) an animal may be starved by giving it continually too simple and too nutritious food; aliment in such a state of condensation does not impart the necessary stimulus, which requires to be partly mechanical and partly chemical, and to be exerted at once on the irritability of the capillaries of the stomach to promote its secretions, and on the muscular fibres to promote its contractions. I shall now point out the difference between the Australian skull and those of some other races, without giving a description of skulls in general, which would unnecessarily lengthen these observations. "Of all the peculiarities in the form of the bony fabric, those of the skull are the most striking and distinguishing. It is in the head that we find the varieties most strongly characteristic of the different races. The characters of the countenance, and the shape of the features depend chiefly on the conformation of the bones of the head." The Australian skull belongs to that variety called the prognathous, or narrow elongated variety; yet it is not so striking an example of this variety as the Negro skull. If the skull be held in the hand so that the observer look upon the vertex, the first point he remarks is the extreme narrowness of the frontal bone, and a slight bulging where the parietal and occipital bones unite. He also sees distinctly through the zygomatic arches on both sides, which in the European skull is impossible, as the lateral portions of the frontal bone are more developed. The summit of the head rises in a longitudinal ridge in the direction of the sagittal suture; so that from the sagittal suture to that portion of the cranium where the diameter is greatest the head slopes like the roof of a house. The forehead is generally flat; the upper jaw rather prominent; the frontal sinuses large; the occipital bone is flat, and there is a remarkable receding of the bone from the posterior insertion of the 'occipitofrontalis' muscle to the 'foramen magnum'. It is a peculiar character of the Australian skull to have a very singular depression at the junction of the nasal bones with the nasal processes of the frontal bone. This may be seen in an engraving in Dr. Pritchard's work. I have before described the teeth, and mentioned the remarkable junction of the temporal and parietal bones at the coronal suture, and consequently the complete separation of the sphenoid from the parietal, which in European skulls meet for the space of nearly half an inch.