420 
NOTES TO THE 
of the above-mentioned plates of bones, with denticulated 
edges, &c. ; while the centre portion of the bone sends down an 
arch to form a canal in which the spinal marrow is contained. 
The tortoise therefore lives inside a house which is composed 
of his own ribs, formed into a dome, and he rests upon his 
sternum or breast-bone, which is flattened out into a broad 
plate to serve, first, for the attachment of the rib, and second, 
as a kind of supporting foot or basement. Can there possibly 
be a more beautiful piece of design than this, which combines 
economy of material and great strength with lightness ? 
We often find the same design in created things utilised for 
various purposes. It is therefore highly interesting to find that 
the same kind of denticulated suture as adopted in the tortoise 
is present also in our own skulls. A bony box is required to 
carry and protect the brain ; the human skull therefore is 
formed of bones, each being joined to its neighbour by iden- 
tically the same kind of union as that in the tortoise. There is 
in the human skull another meaning for this : the interposition 
of several liaes of sutures all over the skull prevents a fracture 
of one of the bones of the skull spreading to its neighbour, 
just as the woodwork in a window-frame prevents the fracture 
of an individual square of glass spreading to the adjoining 
squares. 
Steucture of a Cowl's Horn, p. 136. — It is often the case that 
in the commonest objects we may see (if we like) beautiful examples 
of engineering structures. I take the anatomy of the cow's 
horn as a good example. In the summer of 1874, 1 was inspecting 
the large tanneries of the Messrs. Hamlyn, at Buckfastleigh, on 
the Eiver Dart, Devonshire, to see if any injury was happening 
therefrom to the salmon fisheries. In one of the backyards was 
a mountain of the skulls and horns of cows of all sorts and 
kinds. Here there was a treasure worthy of investigation ; so I 
got on to the mountain of horns and skulls, and picked out some 
beautiful specimens, in order to make sections, &c. 
I find that over the brain of the cow a strong roof of bone is 
thrown, in the shape of an arch, so as to form a substantial 
foundation for the horns. This roof is not solid, but is again 
strengthened below by a series of bony arches, that are so dis- 
tributed as to form a series of hollow chambers, thus forming a 
structure uniting strength with lightness. The problem now is, 
how to fasten the horn on each side on to this buttress. The horn 
itself must of course be formed of horn proper, i.e., hardened 
hair. In the rhinoceros we find a horn composed entirely of a 
solid mass of what is really a bunch of hair agglutinated together] 
