WORKSHOPS AND LABORATORIES 167 



years are reached. By the commencement of the third 

 year a child has got its full set of teeth — twenty in all, 

 ten upper and ten lower. Even then there is being pre- 

 pared at their roots a set which is to replace them and in 

 addition twelve others, which will duly come into place 

 as space is provided behind the milk set. Army 

 manoeuvres which able generals carry out in the field 

 are often complicated operations and difficult of execution, 

 but no army movement can rival the manoeuvres which 

 are to be seen in the mouths of well-grown children where 

 little white soldiers rise up one by one, in the right place 

 and at the right time, to form the upper and lower 

 serried ranks of teeth. But teeth and jaws have fallen 

 on times which, for them, are out of joint. They were 

 designed to do all the milling man required ; nowadays 

 steam-driven machinery and high-class cooking have 

 relieved them of the greater part of their work. We 

 have seen that bone-builders lay down levers according to 

 the stresses and pressures which fall on them when the 

 human machine is in full action ; the bone-builders of the 

 jaws which make up so large a part of our face, have no 

 longer falling on them the stimuli which arise from strains 

 and stresses because their work is being scamped ; the 

 jaws are often ill built, the face tends to become long, 

 narrow, sunken in, in place of being short, wide, and full. 

 In olden days the teeth were often ground down almost 

 to their sockets ; nowadays, even after sixty years of 

 wear, we may observe, in such of them as have survived 

 the modern disease of caries, that their chewing surfaces 

 are scarcely worn. Even the tooth-builders are affected 

 by modern conditions ; their workmanship is not what 

 it was in prehistoric times. Nature is levying the fines 

 she inflicts when her structures are unused. Even with 

 care, cleanliness, and the expert aid of dental surgeons it 

 is difficult to prevent disease attacking our teeth. What, 

 then, is to be done ? Return to the diet of primitive 

 men ? In this case, as in many others, most of us will 

 choose to reap such gains as invention brings within our 

 reach and eat the food which modern skill has succeeded 



