382 THE POPULAR SCIENCE MONTHLY. 



of heat and force, provided that he selects vegetables which contain 

 all the essential elements named. But he must for this purpose con- 

 sume the best cereals, wheat or oats, or the legumes, beans, peas, or 

 lentils ; or he must swallow and digest a large weight of vegetable 

 matter of less nutritive value, and therefore containing at least one 

 element in large excess, in order to obtain all the elements he needs. 

 Thus the Irishman requires ten to eleven pounds of potatoes daily, 

 which contain chiefly starch, very little nitrogen, and scarcely any fat; 

 hence he obtains, when he can, some buttermilk or bacon, or a herring 

 to supply the deficiency. The Highlander, living mainly on oatmeal, 

 requires a much smaller weight, since this grain contains not only 

 starch, but much nitrogen and a fair amount of fat, although not quite 

 sufficient for his purpose, which is usually supplied by adding milk or 

 a little bacon to his diet. On the other hand, the man who lives chiefly 

 or largely on flesh and eggs as well as bread obtains precisely the same 

 principles, but served in a concentrated form, and a weight of about 

 two or three pounds of such food is a full equivalent to the Irishman's 

 ten or eleven pounds of potatoes and. extras. The meat-eater's diges- 

 tion is taxed with a far less quantity of solid, but that very concentra- 

 tion in regard of quality entails on some stomachs an expenditure of 

 force in digestion equal to that required by the vegetable-eater to 

 assimilate his much larger portions. And it must be admitted as a 

 fact beyond question that some persons are stronger and more healthy 

 who live chiefly or altogether on vegetables, while there are many 

 others for whom a proportion of animal food appears to be desirable, 

 if not necessary. In studying this matter individual habit must be 

 taken into account. An animal feeder may by slow degrees become 

 a vegetarian, without loss of weight or strength, not without feeling- 

 some inconvenience in the process ; but a sudden change in diet in this 

 direction is for a time almost equivalent to starvation. The digestive 

 organs require a considerable period to accommodate themselves to the 

 performance of work different from that to which they have been long 

 accustomed, and in some constitutions might fail altogether in the 

 attempt. Besides, in matters of diet essentially, many persons have 

 individual peculiarities ; and while certain fixed principles exist, such 

 as those already laid down as absolutely cardinal, in the detail of their 

 application to each man's wants an infinity of stomach eccentricities 

 is to be reckoned on. The old proverb expresses the fact strongly but 

 truly: " What is one man's meat is another man's poison." Yet no- 

 thing is more common and one rarely leaves a social dinner-table with- 

 out observing it than to hear some good-natured person recommend- 

 ing to his neighbor, with a confidence rarely found except in alliance 

 with profound ignorance of the matter in hand, some special form of 

 food or drink, or system of diet, solely because the adviser happens 

 to have found it useful to himself ! 



It will be interesting now to take a general but brief survey of the 



