to the influence of cooking in diminishing mastication. Dental caries is rare and is chiefly met with in the third molars. 4. _The early agricultural age._--All the existing primitive races which have attained to the cultivation of the soil may be regarded as belonging to this period. Previously to it man was mainly carnivorous, owing to the comparatively limited quantity of vegetable food available, so long as the supply was left to nature alone; but when by cultivation this supply was increased and, at the same time, rendered more constant and certain, he gradually became less carnivorous and more vegetarian in his diet. The result of agriculture, however, is not only to increase the supply of vegetable food, but to diminish its fibrous, cellulosic ingredients, and thus to render it more easily masticated. Hence at this stage we find the maxillary apparatus becoming smaller than in the previous period, although the difference as shown--_e. g._, by the examinations of the skulls of the African negroes and the Melanesians--is less pronounced than we might perhaps have anticipated; prognathism is not so decided, the jaws are smaller, also the teeth, especially the third molars, which now for the first time show a tendency to be furnished with two instead of three fangs, while the alveolar ridge behind them is distinctly shorter than in the preceding period. Dental caries, hitherto rare, now becomes more frequent. 5. _The late agricultural period._--A mid-agricultural period might be described, but I shall take no account of it here, but pass on to a consideration of the late agricultural period--that, namely, in which we ourselves live. The chief characteristic of the food of this period is its softness. Cooked animal food requires, indeed, more mastication than raw, but the vegetable food of to-day, owing to the combined effects of improved agriculture, and skilful milling and cooking, is so soft as to excite comparatively little mastication. The present may, in fact, be described as the _age of pap_. Hence the jaws and teeth are now called upon to perform far less work than in any earlier stage of our evolution, and there has taken place in consequence a great diminution in their size, more especially in the size of the jaws, so that there is now often no room for the teeth to take up their normal positions, and there is generally a complete absence of alveolar ridge behind the last molars. The latter are, moreover, apt to be very small or even absent, while dental caries is alarmingly frequent.