THE MUSCULAP MOTOR AND ALIMENTATION 135 



and zinc (*) seem to serve as cellular " excitants," and have a 

 necessary part in the life of the micro-organisms. 



Man requires from 25 to 30 grammes of sodium chloride per 

 day, which he finds, as well as the other salts, in his food. 



In noticing the essential functions of the different substances 

 which have been mentioned (water, salts), it must be said that 

 they are not true food combustibles. However useful and indis- 

 pensable they may be, their energetic value is nil . A real aliment 

 or food is substance capable of constituting a cellular reserve, 

 and which can eventually develop energy. 



Amongst certain peoples there is found the peculiar custom of 

 eating earthy materials of no alimentary value. This " geo- 

 phagv " is found in Senegal, New Caledonia, Persia, Bolivia, 

 South America and Java. Even in Spain, ( 2 ) eaters of alcaragas 

 (baked earth) are to be found, and the women imagine that it 

 gives them a perfectly white complexion ! It would seem prob- 

 able that the origin ot this peculiar habit is an attempt to provide 

 a mechanical digestive stimulant, as in the case of birds. Dr. 

 Baudouin infers, from the condition of the teeth, that geophagy 

 was a custom among the primitive races of man.( 3 ) 



95. Classification of Food Stuffs. Our aliments are generally 

 complex ; bread is made of " starch " and " gluten," perfectly 

 definite substances to which are given the name of " immediate 

 principles." In the same way meat contains a principle analogous 

 to gluten, derived from starch and fat. Thus an aliment is 

 formed of one or more immediate principles. 



These are of " three kinds." Firstly, sugars and starches, 

 which contain carbon associated with oxygen and hydrogen in 

 the form of " water " ; and are called for that reason " carbo- 

 hydrates." 



Secondly, fats, which also contain carbon, hydrogen and 

 oxygen. 



Thirdly, all the quart ernary principles which contain " azote " 

 or nitrogen as well as the other elements named above. They 



( x ) In this way a mushroom, the Aspergillus niger, forms 1 gramme of 

 vegetable in destroying 3 grammes of sugar, if it develops in a liquid con- 

 taining a trace of zinc. In the absence of this metal, it would take 28 

 grammes of sugar ; the cell then growing less. G. Bertrand has shown in an 

 analagous manner, the effect of manganese and iron, etc (Comptes Rendus 

 Acad. Sciences, 5th Feb., 1912.) 



( 2 ) Hellwald, Ethnogr. Rosselsprunge, Leipzig, 1891, p. 168. 



( 3 ) Comptes Rend. Acad. Sc., 29th Jan., 1912, p. 297. The author admits 

 that the men of the stone age (neolithic period) masticated food containing 

 grains of sand. The geophageous children of the Siamese Laos have to-day 

 teeth worn like those of the children of the neolithic epoch. Geophagy 

 was found by de Humboldt, Biot and Wallot respectively in Lapland, 

 China and certain parts of Germany (Comptes Rend. Acad. Sc., vol. iv., 

 pp. 293, 301, 590, 1837). 



