This working of the jaws would be almost imperceptible excepting to a very close observer. In the lower jaw-bones the independent action can be more readily perceived and is often very grotesque, one side of the mouth opening while the other is closed, conveying the idea of the reptile making grimaces at you; but the gradual disappearance of the prey so much more bulky than the snake itself is quite incomprehensible until we are acquainted with the remarkable phenomena of the six rows of teeth acting independently. Thus, in turning the frog round to adjust it to a more convenient position, the jaws acted like hands in moving, dragging, or shifting some cumbrous article, say a carpet or a plank, when the left hand follows the movement of the right hand until the plank or carpet is worked round or forward in the required direction. The form and arrangement of the fine claw-shaped teeth assist the process. They are too close together, and the pressure is too slight to inflict a wound; they merely retain what they hold, and it is in vain for the prey to struggle against them, or it might get some ugly scratches as they all incline backwards. In chapter xix. illustrations of teeth, life-size, show their forms and direction; here it only need be added regarding them, that the above description refers chiefly to the non-venomous snakes. The palate being covered with that armoury of teeth, the snake must have but a slight sense of taste, which is to its advantage, we should say; for having no assistant in the shape of beak or limbs to divide its prey, hair, fur, feathers, dust—all must be swallowed with the meal, completely disguising whatever flesh they cover, so that we should suppose the process of feeding could be productive of very little enjoyment to the reptile. Perhaps out of this state of things has developed their habit of eating so seldom, but when they do take the trouble of feeding, of doing it thoroughly, so that their meal lasts them a long while. Deglutition is greatly facilitated by an abundant supply of saliva, which lubricates that uncomfortable coating of feathers or fur; but ‘lubrication’ is understood to refer merely to the natural secretions of the mouth, in which the tongue performs no part at all. The salivary apparatus of snakes is peculiar to them, and very complicated. Even the nasal and lachrymal glands pour their superfluous secretions through small canals into the mouth.[4] These active and abundant glands are excited by hunger or the sight of food, just as in mammals; and for the more common expression of the mouth ‘watering’ that of ‘lubrication’ is here used, because over the rough-coated prey these salivary secretions act as a great aid in deglutition. The erroneous impressions that have obtained on this subject are touched upon in describing the tongue (chap. vi.).