A Mechanical Account of Poisons in Several Essays

by Richard Mead

To begin therefore with the Head. The Skull ([Fig. 2.]) is composed of several Bones, joined together by Sutures, as in Man, but with this Difference, that the Os Frontis in the Viper consists of Two Bones united by a Rectilinear Suture, and the Parietal Bones are entire; whereas in Man the Parietal Bones have Sutures, and the Os Frontis is entire.

(a) Shews Two small Semicircular Bones, which form the inferior Part of the Nostrils.

(b) The Two Bones which make the upper Part of the Nose, from the latter pass down two thin Laminæ, which touching one another, and falling perpendicular upon the Ossa Palati, compose the Septum of the Nose.

(e e) Point out the Ossa Frontis, which form the upper Part of the Orbits of the Eyes. And (c c) the Orbits themselves.

The Parietal Bones (d) make a large Cavity, in which the greatest Part of the Brain is contained, and this we may call the Sinciput.

Behind this Bone are placed the Ossa Temporum (f f) in which lye the Organs of Hearring; and behind Them a Bone (g) which, we may call the Os Occipitis, covers the posterior Part of the Brain. This is joined to the first Vertebra of the Neck (h), by a Spherical Articulation, as all the Vertebræ are to one another; and this is the Reason why this Creature can turn its Head and Body so much, and so nimbly, every way.

To some of These there are Two other Bones Articulated for particular Uses.

The First of Them, which serves as a Basis to the Articulation of the Rest (a, [Fig. 4.]), is fastned by one Extremity to a small Proturberance (i, [Fig. 2.]) in the middle and lateral Part of the Os Sincipitis, and running back towards the Vertebræ, lyes in the same Plain with the Sinciput. This Bone has a Motion, tho’ very inconsiderable, both upwards and downwards. By means of This, the opening of the Mouth is somewhat inlarged in the Time of Deglutition.

That End of this Bone, which is next to the Vertebræ, is articulated at oblique Angles with Another (b) placed Horizontally, and whose Motion is forwards and backwards, being made chiefly for moving the Bones of the upper and lower Jaw, into which the Teeth are inserted. By reason of this kind of Articulation, It cannot contribute any thing towards widening the Mouth for Swallowing.

This Bone, and That with which it is joined, I call the Common Bones.