Why? The Science of Athletics

324 WHY?-THE SCIENCE OF ATHLETICS considered, therefore, the best for athletic dietary. It is a moot point whether butter or dripping should he used in any pastry that may be made for athletes. On the whole, perhaps, good, well-clarified dripping is to be preferred to butter, as being the more readily digestible in this particular connection. The average composition of cow's milk Milk is 3·5 per cent protein ; 4 per cent fat ; 4·75 per cent lactose ; mineral matter, 0·75 per c.ent ; and water, 87 ·25 per cent. None the less, the fact that milk is the natural diet of all young mammals when they are growing most rapidly proves the food value of milk. Its suitability is found in its lime salts (calcium) and certain vitamins. A rich supply of lactose takes the place of starch. Milk has casein for its protein, and contains fat in the form of a fine emulsion floating on the surface as cream. The fat constitutes the degree of the milk's fat value, and is the only one of its constituents which varies to any marked degree. When milk is drunk, it virtually ceases to be a liquid, because the rennin, or ferment, of the gastric juices causes the casein of the milk to clot. That is why athletes should not be allowed to gulp down a glass of milk quickly. If too large a clot is formed, digestion becomes difficult. The old-time trainers missed their mark when they held that milk "curdled on the stomach". Clotting and curdling are two entirely different things ; because, as we have seen, it is the gastric juices acting- upon the casein which causes the clot, whereas the curdling of milk is due to the presence in the air of some souring bacteria, which acts upon the milk sugar (lactose) and produces lactic acid, the casein, held in solution by the lime salts, being precipitated. Skim milk, despite its loss of fat, has a high nutritive value, because the c~sein; laCtose and mineral matter still remain. Provided that milk puddings, on account of the farinaceous ingredients, are well cooked, they _are both