February i, 1906] 



NA TURE 



,29 



perfect or improved ; the muscular power of athletes was 

 increased ; mental acuity was undiminished ; and desire 

 of richer food disappeared. 



Chittenden argues from such results (and daily observ- 

 ations were diligently maintained throughout each experi- 

 ment) that his scanty proteid diet is the normal, and that 

 the average meat-eater is the man who is abnormal, ne 

 says : — " Whin we recollect that these eighteen grams 

 or more of nitrogen in the urine reach the final stage of 

 urea, &c, only by passing through a series of stages each 

 one of which means the using up of a certain amount of 

 energy to say nothing of the energy made use of in diges- 

 tion, absorption, &c, we can easily picture to ourselves 

 the amount of physiological labour which the daily handling 

 by the bodv of such amounts of proteid food entails. It 

 needs very little imagination to see that a large amount of 

 energy is used up in passing on these nitrogenous waste 

 products from organ to organ or from tissue to tissue, on 

 the way to elimination, and we can fancy that liver and 

 kidneys must at times rebel at the excessive labour they 

 are called upon to perform." He then goes on to point 

 out that many of these waste products, like uric acid, are 

 toxic, and the evil results that ensue from their accumula- 

 tion. 



It is on such grounds that Chittenden advocates a revolu- 

 tion in our ordinarv dietary, and his arguments for 

 temperance in proteid intake are entitled to careful atten- 

 tion. He is no crank or faddist, and his ctnclusions have 

 been arrived at by the true scientific method, that of 

 experiment. 



There will be many who will pay no attention to them 

 at all. The bon vivant, for instance, will resent any inter- 

 ference with his habits, gout and other evils notwith- 

 standing; and certainly some of the meals Chittenden 

 describes do not appear very appetising ; for instance, a 

 banana and a cup of coffee for breakfast; be;m soup, 

 bread (i oz.), bacon (^ oz.), fried potato, salad, prunes, 

 and another banana for supper. But no doubt variations 

 in the way in which the nutriment can be obtained are 

 possible of introduction. 



The honest inquirer after truth may also have his doubts, 

 and it cannot be disputed that there are difficulties, and 

 serious ones, which will have to be answered before the 

 advocacy of the new idea will meet with success. 



One would like to know, for instance, whether the 

 numerous subjects of the experiments are still keeping up 

 their reduced diet, or whether they have returned to the 

 flesh-pots after a period of enforced abstinence. If they 

 are still maintaining their new habits, one would like to 

 know how they fare in a few years' time, if they have 

 the reserve force to enable them to withstand a severe 

 disease, great fatigue, or privation during a siege, and 

 whether the initial briskness they felt when they dropped 

 their large (probablv too large) proteid intake is main- 

 tained, or whether, on the other hand, they present the 

 appearance and svmptoms of underfed persons. 



A cautious and conservative person would point to the 

 danger of a sudden change in the habits of years and 

 generations, even though it may ultimately be necessary. 

 Most physiologists will recall the analogv of metabolic 

 changes to commercial undertakings which they employ 

 when presenting balance-sheets of intake and output in the 

 body, and say, just as in a business enterprise, a large turn- 

 over implies healthy activity, so in the body a frequent 

 exchange of the old for the new is within certain limits an 

 indication of vigour, and a necessary accompaniment of 

 healthy action. The liver, the function of which it is to 

 turn nitrogenous metabolites, which may be harmful, into 

 urea, which is harmless and easily disposed of, is adequately 

 large and active in health to deal with considerable quanti- 

 ties of material. 



Then we may point to the stunted and feeble inhabitants 

 among the poor and ask why they are so. Unhealthy 

 dwellings, excess of alcohol, insufficiency of light and pure 

 air will explain a good deal of their condition ; but is it 

 not underfeeding, especially in early life, which is at the 

 root of the matter? They have had nolens volcns to subsist 

 on a diet very like Chittenden's, but their nutritive condition 

 is not such as to make people who can afford a mere liberal 

 table inclined to follow their example. 



Further, one may inquire, why is it that, with a few 



NO. 1892, VOL. 7$} 



exceptions, the meat-eating nations have risen to the front? 

 and why is it that in countries like India, where the native 

 population is diluted with the white races, it is the former 

 who are more readily attacked by disease, and more easily 

 succumb to its effects? 



A question intimately related to that of a suitable diet 

 for the healthy adult is that of the feeding of children. 

 The diet of the growing infant is relatively far richer in 

 proteid than that of the adult. Must we also reduce the 

 intake of proteid food in the child? This is a question 

 that Chittenden has not touched, but clinical experience 

 does not point, so far as I can ascertain, to an affirmative 

 answer, either with regard to the feeding of infants or of 

 certain classes of invalids. 



These questions and difficulties cannot be answered off- 

 hand. There is a wide field still open to investigators, 

 and not until such difficulties are removed will it be possible 

 for physiologists to state that Prof. Chittenden has con- 

 vincea them. 



The Work vf Folin. 



Whether Dr. Otto Folin has seen these difficulties or 

 not, he certainly does not mention them, and he appears 

 as an advocate of the new doctrine, not only from a study 

 of Chittenden's investigations, but also as a result of his 

 own researches. Nitrogen enters the body in the complex 

 compounds known as proteids ; it leaves the body mainly 

 by the urine in the shape of certain simpler substances of 

 which urea is the most abundant. F'olin has approached 

 the subject from the aspect of nitrogenous discharge, and 

 has published his investigations on the urine in a series of 

 three interesting papers in the American Journal of 

 Physiology (vol. xiii., 1905, pp. 4s-&5, 66-115, 117-138). 

 Although it is possible that some of his conclusions mav 

 not stand the test of time, all of them are most suggestive, 

 and his theory of proteid-metabolism will stand out as one 

 of the most important contributions to physiological litera- 

 ture that has appeared within recent times. 



The question, what is a normal diet? is intimately 

 bound up with another, and that is, what is a normal 

 urine? The text-book statements on the composition of 

 this fluid are all derived from the examination of the urine 

 of people accustomed to the Voit dietary ; but if the diet 

 of the future is to contain only half as much proteid, the 

 urine of the future will naturally show a nitrogenous out- 

 put of half that which is now regarded as normal. In 

 people on such reduced diets, Folin shows that the decrease 

 in urinary nitrogen falls mainly on the urea fraction, and 

 in some cases the urea accounted for only 66 per cent, 

 of the total nitrogen eliminated. The other nitrogenous 

 waste products alter but little in absolute amount, but 

 relatively their amount rises ; in particular, the creatinine 

 remains remarkably constant in absolute amount in spite 

 of the great reduction in the proteid ingested. He goes on 

 to point out that the laws governing the composition of 

 urine are the effect of more fundamental laws governing 

 proteid katabolism. Voit's well known theory on this 

 question states that katabolism, i.e. the breaking down 

 stage, occurs only in "circulating proteid "; the small 

 amount of " living proteid " which dies is dissolved, and 

 is then added to the " circulating proteid," where the final 

 breakdown into waste products takes place. Pfluger, on 

 the other hand, believes that all proteid taken in as food 

 is first assimilated and becomes a corporate part of living 

 cells before it undergoes the katabolic change. This view 

 has met with more general acceptance than Voit's. The 

 opinion held by Folin is that neither of these extreme views 

 is correct, but that nitrogenous katabolism is of two kinds : 

 one is inconstant and immediate, varies with the food, 

 and leads to formation of urea and inorganic sulphates, but 

 not of creatinine and " neutral sulphur." The other is 

 smaller in amount, constant in quantity, and is largely 

 represented by creatinine, "neutral sulphur," and to a 

 less extent by uric acid and ethereal sulphates. This. latter 

 form of metabolism, representing the breakdown of actual 

 living substance, may be termed tissue or endogenous 

 metabolism, whilst the other is exogenous. Exogenous 

 metabolism therefore represents an immediate discharge of 

 the nitrogenous constituent of proteid matter, leaving the 

 non-nitrogenous moiety available for use in heat and 

 energy production, fulfilling, in other words, the same func- 



