808 



DIET 



out the use of carbohydrates. The Eskimo and 

 the North American Indian live entirely on the 

 produce of the chase. The flesh of animals is rich 

 in proteids and fats, but contains practically no 

 carbohydrate. In the same way the Arab or the 

 desert lives upon the flesh and milk of the camel, 'in 

 districts where the date is not to be found. The 

 use of carbohydrates is extensive in most temper- 

 ate and tropical climates. Many of the inhab- 

 itants of India and Ceylon live chiefly on rice. 

 Wheat, potatoes, and other vegetable foods, rich in 

 carbohydrates, are staple articles of food both in 

 Europe and America. In fact, within certain 

 limits, man, like every other animal, is capable of 

 adapting himself to the food produced by the 

 district in which he lives. The French and Spanish 

 peasants eat little meat, living on carbohydrates 

 and vegetable proteids, and supplying necessary 

 potential by an abundance of oil. The Sussex 

 labourer consumes his beans, rich in vegetable 

 proteids, and bacon, and does a good day's work on 

 them. The Scotch labourer of a former generation 

 lived on porridge and skimmed milk, with meat 

 but once a week. The Arab of the Sahara, 

 together with his family and his horse, subsist 

 almost entirely on the date, while the Arab of the 

 Nubian Desert hardly ever touches vegetable food. 

 The diet of every man, under whatever circum- 

 stances, invariably contains proteids, although this 

 may vary in its quantity. The universal use of 

 proteid matter in some form or other suggests its 

 importance, and this is fully borne out by the 

 evidence of direct experiment. If proteid food be 

 withdrawn from the diet altogether, nitrogenous 

 matter continues to be eliminated from the body by 

 the urine, although its supply is cut off. At the 

 same time the body wastes, and death finally occurs. 

 The experiments of Fick, Wislicenus, and Parkes 

 show that during muscular exertion the body does 

 not excrete any excess of nitrogen ; and the writer's 

 own researches show that urea the most important 

 excretion which contains nitrogen is not found in 

 abnormal extent in muscular tissue after exhaustive 

 exercise. It would appear, therefore, that nitro- 

 genous matter is not used by the tissues for fuel, 

 and that when proteid food is consumed, the 

 muscles burn a non-nitrogenous substance which 

 is formed from it. The nitrogen, in the form of 

 urea, &c., is carried by the blood to the kidneys, 

 and at once excreted. We must look elsewhere 

 than in the ordinary combustion of a muscle or 

 brain cell for a use for the nitrogen which, as we 

 have seen, is so necessary an article of food in the 

 form of a proteid substance. In the child, the 

 tissues which contain nitrogen in definite pro- 

 portion are continually growing, and it will readily 

 be seen that here, at anyrate, we have an import- 

 ant use for proteid diet namely, to furnish the 

 necessary nitrogen for the new tissue. Even dur- 

 ing adult life we have tissue change and growth. 

 The skin is continually growing in its deeper layers 

 to replace its surface layers worn away by constant 

 friction. In the same way the cells of the blood 

 are always being broken down, and their places 

 taken again by new ones continually forming. 

 Although it is hardly probable that such complete 

 changes take place in all the tissues of the body, 

 yet, without the entire breaking down of individual 

 cells, there are no doubt changes both integrating 

 and disintegrating, which are constantly taking 

 place. As a result of disintegrating changes nitro- 

 genous matter in an effete form is being given off 

 by the system, and it has to be replenished from 

 without in a form which the body can use. The 

 proteid food-stuff provides nitrogenous pabulum for 

 the tissues which they assimilate, and build up new 

 tissue material. For this reason proteid matter is 

 indispensable. At the same time the system obtains 



from the proteid food non-nitrogenous fuel to be 

 burned by the tissues ; this property of supplying* 

 tissue fuel is shared with the carbohydrate and 

 fatty food-stuffs. It has been found by experiment 

 that an ordinary diet should contain one part of 

 nitrogenous matter (proteids) to about four of non- 

 nitrogenous diet (fat and carbohydrates). If less 

 nitrogenous matter be given, the tissue consump- 

 tion of nitrogen will not be supplied, and the body 

 will waste. If a much larger quantity of nitro- 

 genous food be taken, a nitrogenous surfeit occurs, 

 and the body is called upon to digest this excess, 

 and to eliminate an unnecessary quantity of the 

 useless nitrogenous compounds which result. 



We have seen then that an ordinary diet must 

 contain sufficient potential, and in addition one 

 part of proteid to four of non-proteid material 

 should be present. The following table from Dr 

 Parkes shows the proper proportions of solid water- 

 free food-stuffs in ounces required as daily food by 

 an adult man : 



At Rest. Ordinary Work. Hard Work. 



Proteids 2'5 4-6 6 to 7 



Fats 1 3 3'5 to 4'5 



Carbohydrates 12 14-4 16 to 18 



Total water-free food.. 15-5 



22-0 



25-5 to 29-5 



Taking the diet table for a man performing 

 ordinary work, we have 4 - 6 of proteid, and 17*4, or 

 nearly four times as much non-proteid matter. It 

 contains sufficient potential, for if the number of 

 foot-tons which result from the combustion of an 

 ounce of proteid, of fat, and of a carbohydrate be 

 multiplied by the number of ounces of these sub- 

 stances given in the ordinary diet, it will be seen 

 to amount to 4000. This, as we have already seen, 

 indicates a sufficient potentiality. 



It now becomes an easy matter to construct a 

 diet table of articles of food. Most of these have 

 been analysed, and the amount of water, proteid, 

 carbohydrate, or fat in each calculated. 



TABLE FOR CALCULATING DIETS (Parkes). 



Many articles of food owe their chief importance 

 to their action as stimulants. Such are alcohol, tea, 

 coffee, and beef-tea. Alcohol is no doubt burned 

 within the body, and is a source of energy. Only a 

 small quantity, however, can be so utilised, perhaps 

 one ounce in every twenty-four hours in the case of 

 an ordinary individual. As a source of energy, 

 therefore, it is of little value, and such substances 

 as fat, meat, bread, are capable of supplying the- 



