(b) The skull.—Feel the bones of the head through the skin, and make out the rounded brain-case, the ridge above and the arch below each eye, and the positions of the jaws. (c) The external ears.—Examine the large ear-flaps. Notice that the upper parts are thin and almost transparent, and that the lower parts are gristly and lead into the interior of the head. (d) The eyes.—Notice that the eyes are at the sides of the head. Is this position an advantage to the rabbit? Examine, in each eye, the upper and lower lids; and also, in the angle of the eye next the nose, the third eyelid—a fold of white skin. Take hold of this fold with the forceps and see that it is easily pulled over the eyeball. Look in a mirror and see the little fleshy body which occupies a similar position in your own eye; this corresponds to the rabbit’s third eyelid. In the visible part of the rabbit’s eyeball notice the round dark pupil in the middle (contrast the pupil of a cat’s eye); the coloured ring (the iris) surrounding the pupil; and the “white” (called the sclerotic) surrounding the iris. (e) The lips and nostrils.—Notice how the upper lip is split in the middle line, so as to show the front teeth. What is the use of the split? Notice the grooves passing from the upper lip to the nostrils. [Pg 213] (f) The inside of the mouth.—Open the rabbit’s mouth and notice: (i) The two gnawing or incisor teeth in the lower jaw, and the pair of strongly-grooved incisors which are so conspicuous in the upper jaw. Just behind the large, upper incisors two smaller incisors may be felt with the finger. Separated by a wide space from the incisors are the grinding teeth—six on each side in the upper jaw, and five on each side in the lower jaw. (ii) The tongue, lying between the halves of the lower jaw. (iii) The hard ridges running across the fore half of the roof of the mouth. (iv) The hairiness of the inside of each cheek, between the incisor and grinding teeth. 4. The neck.—Notice how the neck enables the head to be turned freely in various directions without the body being moved. Feel through the skin and identify: (a) In front of the neck, the trachea or windpipe, with the larynx or “voice box” at its upper end between the halves of the lower jaw. (b) The bones of the neck-part of the spine. 5. The trunk.—Feel through the skin and make out the spine, the breast-bone, and the curved ribs which connect these. The spine, breast-bone, and ribs together form a bony cage which encloses the fore-part (the thorax) of the body. The hinder and larger part of the body (the abdomen) is not protected by ribs, but the bones of the spine are largest and stoutest in this part of the body.