MASTICATION.

King Country Chronicle, Volume VII, Issue 586, 19 July 1913, Page 3

MASTICATION.

. By Dr Harry Campbell.

EVOLUTION OP JAWS AND TEETH. Inasmuch as before man learnt to break up the cellulose framework of hia vegetable food by cooking, grinding, and other 'means, he was compelled to make vigorous use of his masticatory apparatus we may be sure that in the pre-cookery period this was correspondingly strong and massive,b ut when the discovery of artificial means of disintegrating the cellulose (grinding and cooking) mastication was in great measure relieved of one of its chief functions, the jaws and teeth began to get smaller, while dental cares, hitherto unknown, became less rare, invading chiefly the third molars (wisdom teeth). Again, as the effect of agriculture was to reduce the cellulose ingredients of vegetable food and thus to render it more easy of mastication, we find the jaws and teeth further diminishing in size during this next period, and diseases of the teeth increasing in frequency. These effects were not, however, pronounced during the early agricultural epoch, partly because man still continued to eat freely of raw vegetable food,and partly also because much of its cooked vegetable food, needed, owing to its coarseness, considerable mastication. It is not until we arrive at comparatively recent times that the effect upon the jaws and teeth of food artificially produced and prepared becomes pronounced. The present-day vegetable food—in our own country, at east — owing to the combined effects of im proved agriculture and skilful milling and cooking, is so soft that it excites comparatively little mastication. We live, in fact, in fin age of pap. Hence the modern jaw ia undergoing considerable diminution in size, with the result that the teeth which are not diminishing in number at the same rate, are often unable to take up their normal positions, while dental diseases have asaumed truly alarming proportions. THE INSTINCT TO MASTICATE. During the first month? of life of life the natural function of feeding at the breast provides the infant's jaws, tongue, and lips with all the needful exercsie. Bottle-feeding fails to do this, and in consequence we frequently find bottle-fed children seeking to satisfy their natural inßtinct to use those structures by sticking their fingers on other convenient objects. (Memo, by Hgyieia.— The best of bottle-feeding is inferior to suckling in regard to the work done during feeding, but if proper care is taken the mother can ensure that her baby shall "work for his living," and must not merely imbibe his food in a pansive way. The smaller the hole in the indiarubber nipple the better, provided the baby can be brought to work hard enough to secure sufficient milk in from a quarter of an hour to twenty minutes. This can be effected by the mother holding the bottle and keeping a slight tension on it, and moving thu teat about so'that the baby's mouth is properly stimulated and has something to tug at. Thus, starting with the muuth, the whole system o£ the baby ia set hard at work —nerves, muscles, circulatory, breathing, and digestive organs busily doing their appointed tasks. The long-tube feeder is one of the worst enemieß of the modern baby. There is nothing to pull on, and the baby simply imbibes ita food without appreciable stimulus or exerCISC'GIVE BABY A BONE. The teeth are a provision for biting hard foods, but even before they actually appear the child tries to exercise hia toothless gum? on any bard substance upon which he can lay hold, and there can be no doubt that its so doing tends to facilitate the eruption of the teeth, a truth which is, indeed, universally recognised, whether by the primitive mother who hangs the tooth of some wild beast round the neck of her infant, or the up-to-date one who provides hers with a bejewelled ivory or coral bauble. As soon as the teeth have been cut the masticatory instinct has among primitive peoples abundant scope in the chewing of the coarse, hard foods which consttute their dietary; but in as moderns, subsisting as we do mainly on soft foods, it does not find its proper expression, and thuß ends to die out. Neverteless, it dies a bard death, and long continues to assert itself; witness the tendency of children to bite their pencils and penholders and to chew small pieces of indiarubber for hours together. I have known a child to gnaw through a bone penholder much in the same way aB a carnivorous animal gnaws at a bone. I may allude in pasßing to the grinding of the teeth which takes place during sleep in diaturbed states of the nervous system. It iB a true masticatory act, in which'the normal lateral grinding movement of the lower jaw ia well marked, and it may thus be regarded as a perverted manifestation of the masticatory instinct.