88 THE CHEMISTRY OF FOOD 



29. Necessity of a Regulated Diet. A great variety of ex- 

 periments have been tried, in order to test the relative value 

 of the different nutritive principles. They have been practised 

 to some extent upon man, but chiefly upon those inferior 

 animals which require a similar diet to man. 



30. By this means it has been demonstrated that first, 

 when any one of these substances is eaten exclusively, the 

 body is imperfectly nourished, and life is shortened. Dogs fed 

 exclusively upon albumen, fat, or -sugar, soon die of star- 

 vation. Second, a diet long deprived of any one of these 

 principles is a fertile cause of disease ; for example, on ship- 

 board, where fresh vegetables are not dealt out for a long 

 period, scurvy becomes prevalent among the sailors. They are, 

 however, to a certain extent mutually convertible, and thus 

 the missing article is indirectly supplied. For instance, sugar 

 changes to fat in the body ; and hence, as is well known, the 

 " hands " on a sugar .plantation grow fat during the sugar season 

 by partaking freely of the ripened juices of the cane. (Bead 

 Note 11.) 



31. That is the best diet, therefore, which contains some of 

 each of these principles, in due proportion; and that is the 

 worst which excludes the most of them. The cravings and 

 experience of man had unerringly guided him to a correct 

 regulation of his diet, long before the chemistry of food was 

 understood; so that his ordinary meals long ago combined 



11. The Effects of a Poor Diet "The food of the poor in olden 

 times was poor and scanty ; so much so, in fact, that their pqwers of life 

 were depressed ; and we believe this fact had much-to do with the fearful 

 mortality of the plague throughout Europe during the middle ages. The 

 lower classes, especially those living in crowded cities, and subsisting on 

 the scanty and monotonous diet that the historians of the period describe, 

 were the principal sufferers. From 1296 to 1666, hundreds of thousands 

 were carried off by the most fearful pestilences the earth has ever known. 

 Rye in France and oats in England were for generations the almost exclu- 

 sive diet ; wheat was a luxury, which even the rich might only indulge in 

 at Christmas. Oats were known in Germany 2,000 years ago, and were 

 probably the original bread-grain for all Europe." Dr. J. Knight. 



29. What is said of experiments that have been tried ? 



30. What has been demonstrated in the first place ? Example ? Second demonstra- 

 tion ? Example ? Give the illustration in relation to convertibility. 



