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 Metabolisn of Nitrogen and CarVon in the Human Organis: 
 
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 Bulletin No. 44. 216 
 
 U. S. DEPARTMENT OF AGRICULTURE. 
 
 OFFICE OF EXPERIMENT STATIONS. 
 
 REPORT 
 
 OF 
 
 PRELIMINARY INVESTIGATIONS 
 
 ON THE 
 
 METABOLISM OF NITROGEN AND CARBON 
 IN THE HUMAN ORGANISM, 
 
 WITH 
 
 A RESPIRATION CALORIMETER OF SPECIAL CONSTRUCTION. 
 
 BY 
 
 W. 0. ATWATER, Ph. D., C. D. WOODS, B. S., and P. 6. BENEDICT, Ph. D. 
 
 • 
 
 WASHINGTON: 
 
 GOVERNMENT PRINTING OFFICE. 
 18U7. 
 
 
 
Bulletin No. 44. 
 
 U. S. DEPARTMENT OF AGRICULTURE. 
 
 OFFICE OF EXPERIMENT STATIONS. 
 
 REPORT 
 
 OF 
 
 PRELIMINARY INVESTIGATIONS 
 
 ON THE 
 
 METABOLISM OF NITROGEN AND CARBON 
 IN THE HUMAN ORGANISM, 
 
 WITH 
 
 A RESPIRATION CALORIMETER (IE SPECIAL CONSTRUCTION. 
 
 W. 0. ATWATER, Ph. D., C. D. WOODS, B. S., and F. G. BENEDICT, Ph. D. 
 
 WASHINGTON: 
 
 GOVEKXMKNT I'l'tf.VTINt; OFFICE. 
 I.SD7. 
 

LETTER iW TRANSMITTAL. 
 
 U. S. Department of Agrkjultitrb, 
 
 Office of Experiment Stations, 
 
 Washinytoii, I). C, 'June W, i.s'.V7'. 
 
 Sir : I have the honor to trausniit herewith a report of iuve.sti.ua- 
 tioii.s ou tlie inetabolism of man, in the conduct of which a respiration 
 calorimeter of special construction was used. The experiments with 
 nii'ii herein reported were made in the winter of 1895-90, at Middle- 
 town, Conn., under the immediate supervision of Prof. W. O. Atwater, 
 special agent in charge of nutrition investigations. These experi- 
 ments were, liowever, only made i)ossible by previous researches with 
 si)ecial reference to the development of the apparatus and methods of 
 intpiiry. 
 
 This work was begun in 18915 under the direction of Professor 
 Atwater in connection with his duties as professor of chemistry in 
 Wesleyan University and director of the Storrs Agricultural Experi- 
 ment Station. Prof. E. 1>. liosa, of Wesleyan University, was asso- 
 ciated with the incpiiry, on the physical side, from the outset. When 
 investigations on the food and nutrition of man were undertaken by 
 this Department in the fall of 1894, exi)eriments with the respiration 
 calorimeter were made a part of the general plan of work, and it was 
 decided to extend financial aid to these special investigations, which 
 were already well advanced and gave i)romise of successful issue. 
 Since that time these iinjuiries have been conducted by the cooperation 
 of this Department, the Storrs Experiment Station, and Wesleyan 
 University. In this way, by the expenditure of conjparatively small 
 sums for the [)romotion of this particular investigation, the De[)artment 
 lias been able to secure for publi(;ation the results of a large amount of 
 original research in a line of vital importance in connection with the 
 establishment of a scicntilic basis for the nutrition of num. The work 
 on the res])iratiori calorimeter was far enough advanced by the winter 
 of lS9.">-90 to justify its use in experiments with men. After several 
 preliminary trials, the data from which were too incomplete to warrant 
 publication, but which were of great service iti i)erfecting arrangements 
 for the succeeding trials, the four experiments reported in this bulletin 
 were made. 
 
 NN'hile all tlu; details of these experiments are not yet ])erfe(;tly satis- 
 factory and there is still room for further injprovement of the apparatus 
 to be used in sue!) intricate investigations, they nevertheless mark a 
 
decided advance over work of similar character hitherto published 
 and give great encouragement to continued researches in this line. 
 
 The greatest success thus far has been in the measurement of the 
 metabolism of nitrogen and carbon, and the present report is devoted 
 chiefly to the chemical side of the investigation, which includes these 
 measnremeuts. When these experiments were made the work on the 
 physical side, although carried on with great skill and with highly 
 interesting results, had not given data sufficiently accurate in all their 
 details to make its publication seem advisable. The investigations are 
 proceeding, changes in tbe apparatus have already resulted in very 
 satisfactory physical measurements, and it is hoped befoi^e long to pub- 
 lish more complete data on both the physical and chemical sides of the 
 work. 
 
 The general management of these investigations has devolved upon 
 Professor Atwater. In devising and elaborating the apparatus and in 
 the carrying out of that part of the investigation which relates to the 
 measurement of the heat given off from the body and the mechanical 
 work done. Dr. E. B. liosa, professor of i)hysics of Wesleyan Univer- 
 sity, has rendered invaluable service. It is expected that in later 
 reports Professor Kosa will appear as joint author in the discussion of 
 the investigations from the physical standpoint. On the chemical side, 
 Dr. Atwater has had the assistance of Prof. O. D. Woods and Dr. 
 F. G. Benedict, joint authors of this report. The skill and ingenuity 
 of the university mechanician, Mr. O. S. Blakeslee, have also contrib- 
 uted in no small degree to the practical embodiment and successful 
 working of the various devices adopted for the perfecting of the aj)pa- 
 ratus. Other workers whose services deserve special recognition are 
 A. W. Smith, O. F. Tower, A. P. Bryant, and H. M. Burr. 
 
 This report is respectfully submitted, with the recommendation that 
 it be published as Bulletin No. 44 of this Oftice. 
 Eespectfully, 
 
 A. C. True, 
 
 Director. 
 
 Hon. James Wilson, 
 
 JSecretary of Agriculture. 
 
CONTENTS. 
 
 Page. 
 
 iNTUt )nrcTiox 7 
 
 ( loueral statement 7 
 
 The experiments reported in tliis bulletin 10 
 
 ArPAUATUS 11 
 
 The resi)iiatiou ehaniher 12 
 
 Appliances for ventilation and for the measurement and analysis of the 
 
 ventilatiui,' current of air 16 
 
 Air pump 18 
 
 Tension equalizer !!• 
 
 Meter for measuring air 19 
 
 Aspirators for sampling air 20 
 
 Apparatus for determining earbon dioxid and water in sniuples of air. 21 
 
 Methods ov samplixh ani> analysis 22 
 
 Analysis of food, feces, and urine 22 
 
 Preparation and sampling of food 22 
 
 Water.. 24 
 
 Fat — Ether extract 25 
 
 Ash 25 
 
 Nitrogen — Protein 25 
 
 (Jarbon and hydrogen 26 
 
 Heats of combustion — Fuel values 26 
 
 Collecting, jjreserving, and sampling of feces and urine 26 
 
 Analysis of respiratory pioducts 27 
 
 Carbon dioxid 27 
 
 Water 20 
 
 Volatile organn- compounds 31 
 
 The experiments 31 
 
 The diet 32 
 
 Daily routine 31 
 
 Computation of icsults 35 
 
 Nitrogen l)a]an<e 35 
 
 Carbon lialance 37 
 
 Cain ami loss oi' jiroteiu aTid fat 3S 
 
 Energy 39 
 
 l{espiration experiment No. 1 (Digestion experiment No. 11) 40 
 
 Respiration <-xperiment No. 2 (Digestion experiment No. 12) 45 
 
 Respiration experiment No. 3 (Digestion expeiiment No. 13) 4S 
 
 Respiration experiment No. 4 (Digestion expf^rimeut No. 14) 51 
 
 1 MscuHsion oC rr-snlts 56 
 
 V^cntilatioii and jiroduction of earbon dioxid 5(5 
 
 Nutrients :ind (nel \ iilues 5.S 
 
 Conclusions 63 
 
ILLUSTRATIONS. 
 
 Pajre 
 Fig. 1. Eespiration calorimeter 11 
 
 2. Plau of rt'spiration calorimeter room , 13 
 
 3. Elevation of respiration ealorimeter room 15 
 
 4. Outline sketch of respiration apparatus 17 
 
 6 
 
METABOLISM OF NITROGEN AND CARBON IN THE HUMAN 
 
 ORGANISM. 
 
 INTRODUCTION. 
 
 Ill order to ascertain the vvuy.s in which food is used in tlie body and 
 the kinds and amounts which are best suited to people of different 
 classes and under ditti^rent conditions it is necessary to devise accurate 
 methods of determining^ the total income and out^o of material and 
 energy in the organism. The importance of such a study of the funda- 
 mental xmnciples of nutrition luis been recognized for nuuiy years, and 
 studies of one or more of the factors of the income and outgo (espe- 
 cially of nitrogen) have received much attention by investigators in 
 this field of science. In experiments of this nature it is customary to 
 express the results as a balance, in which the outgo is subtracted from 
 the income, thus showing the gain or loss. 
 
 GENERAL STATEMENT. 
 
 So far as the balance of material is concerned, the income consists of 
 food, drink, and oxygen of inhaled air; and the outgo consists of feces, 
 urine, and the products of resi)iration and perspiration. A complete 
 ex]»eriment on the metabolism of material would involve determiimtions 
 of the total amount of oxygen consumed, the amounts and tlie elemen- 
 tary and ])roximate composition of food, feces, urine, and products of 
 respiration and perspiration (including marsh gas from the intestines, 
 and similar products). For the balance of energy, the income would 
 include the potential energy of the food and drink; the outgo wfmld 
 inchide the potential energy of feces and urine, jtroducts of resi)iration 
 and |)erspiration, and the kinetic energy given off in heat from the 
 body ami the medianical <mergy of the external muscular work per- 
 formed. It is possible that other less familiar forms of energy may be 
 concerned, but these are all which are at present known and which 
 may be measured. Due account must of course be taken of the tem- 
 j)erature and specific heats of food, drink, ami excretory ])roducts, aiul 
 the h(;at used or evolved in the condensation of the watei- of exhalation. 
 
 A complete metabolism e\perinu*nt would involve, therefore, the 
 determination of the following factors of income and outgo of matter 
 and energy: 
 
 Factor X of income. 
 
 Matt<!i': I'ood, drink, ox.vf^eii of iiir. 
 
 KleriH-.rifH of food, driiift, and air: N, C. 11, O, S, P, CI, K, Na, Mg, Ca, Fe. 
 (.*om|;oundH of food and drink: Water, jtrotcin fompoinids, fatu, carbohy- 
 diat'-H, anri mineral niatterH. 
 Energy: Potential energy of (organic) corripoiinds of fi)o<l ami (iiiiil<. 
 
 7 
 
Factorfs of outgo. 
 
 Matter: Feces, urine, products of respiration and perspiration. 
 
 Elements of above: N, C, H, O, S, P, CI, K, Na, Mg, Ca, Fe. 
 Compounds: Water of urine and feces; carbohydrates and mineral matter 
 of feces; organic and mineral compounds of urine; COj, H.2O, and organic 
 compounds, etc., of products of respiration ard perspiration. 
 Energy: Potential energy of (organic) compounds of feces, urine, and products of 
 respiration and perspiration. 
 Kinetic energy given off from the body, as beat, external muscular work, 
 and possibly in other forms. 
 
 Tbe above statement is, liowever, incomplete in tliat it does not 
 take into account the material which the body gains or loses during 
 the experiment and the corresponding energy stored or transformed. 
 This material consists mainly of water, protein compounds, and fats, 
 with smaller amounts of carbohydrates, mineral matters, and other 
 compounds. 
 
 The above factors represent the gross income and outgo. The net 
 income would include only the material wiiicli the body actually util- 
 izes from food, drink, and air; that is, it represents the income of nutri- 
 ents, water, and energy consumed minus the unassimilated jiortion 
 excreted iu the feces, taking into account also the incomjdetely oxi- 
 dized matter iu the urine, Tlie net income of material is that which is 
 taken into tlie circulation, builds and repairs tissue, and yields energy. 
 The net income of energy is the jiotential energy of this ]naterial plus 
 the energy received with the food and drink in the form of heat. 
 
 The gross outgo includes the total material of the excretory products, 
 and the sum of their potential energy and the kinetic energy given off 
 from the body. The net outgo is made up of the excretions of the kid- 
 neys, lungs, and skin, and the sum of their potential energy and the 
 kinetic energy given off from the body. The material and the poten- 
 tial energy of the feces are not utilized, but simply rejected.' 
 
 Metabolism experiments may include the measurement of the income 
 and outgo of one or more of the above factors. Wlien the balance of 
 nitrogen, with or without mineral matter, is determined, the only fac- 
 tors of outgo which enter into account are the urine (sometimes includ- 
 ing the perspiration) and feces, since no considerable amount of nitro- 
 gen or mineral matter is believed to be excreted in any other form. 
 When the balance of carbon, wath or without oxygen and hydrogen, is 
 determined, the products of respiration and perspiration must be taken 
 into account in addition to the urine and feces. Experiments of this 
 nature are commonly called "respiration experiments." The experi- 
 ments reported here are respiration experiments, devoted especially to 
 the determination of the income and outgo of nitrogen and carbon. 
 
 iThe residues of digestive juices and other so-called metabolic products of the 
 feces are, it is true, a part of the material which has been digested, absorbed, and 
 metabolized, but they represent material which is neither utilized for building or 
 repairing organs or tissue, nor consumed to yield energy, and which, therefore, may 
 here be classed with the undigested residue of the footl. 
 
9 
 
 Investigation regarding the metabolism of matter in animals and 
 man Las been very active during the last forty and especially tbe last 
 twenty years. Indeed the experimental results already obtained in 
 this direction are much more extensive than is commonly supposed. 
 A compilation' has recently been prepared by this office whicli it is 
 believed includes the greater part of the experiments with man and 
 the lower animals in which the balance of income and outgo of one or 
 more chemical elements has been determined. Tlic nnnd)er of experi- 
 ments in which the income and outgo of energy has been measured is, 
 however, extremely small. 
 
 A review of this work made it evident that research upon nutrition 
 liad reached a point where more study of tlie ai)plication of the laws of 
 the conservation of matter and of energy in the living organism was 
 essential. It is not enough to know the kinds and amounts of food 
 consumed as they are shown by dietary studies, or the i)roportions that 
 arc digested as they are learned from digestion ex])eriments, or the 
 general effects of food materials as they are brought out by ordinary 
 feeding trials. Exi)eriments in which the balance of income and outgo 
 of nitrogen are learned by weighings and analyses of food and of the 
 secretions of the kidnej^s and intestine are extremely useful, but never- 
 theless inadequate. The balance of income and outgo of the body must 
 l)e deterniined both in terms of matter and of energy. For this pur- 
 pose a respiration ai)paratus which measured only the income aiul outgo 
 of matter would not suffice. There was need of an apparatus in whicli 
 an animal or a man may be placed for a number of hours or days and 
 tlie amounts and composition of the food and drink and inhaled air, the 
 amounts and composition of the excreta (solid, liquid, and gaseous), the 
 ])Otential energy of the materials taken into the body and given off 
 from it, the (piantity of heat radiated from the body, and the mechani- 
 cal equivalent of the muscular work performed could all be determined. 
 
 Kesi)irati<m apparatus of various sorts have been devised by a niiin- 
 l»er of investigators. They may, perhaps, for (!onvenieii(;e, be divided 
 into three classes: (1) Those in which the subject remained in a closed 
 chamber and was su])plied with oxygen to take the jilace of that witli- 
 <Irawn from the air by the processes of respiration. The air in the 
 (chamber was aiialyz(Ml at the beginning and end of the experiment, 
 (li) Those in wiiich the subject remained in a. chamber supplied with a 
 (Mirrent of air which was measured and analyzed as it entered and left 
 tlie ehandter. (.'{) Those! in whicdi the subject did not icmain in a 
 ehamher, hut was jn'ovided with api)aiatus wiiich iiermitted the nu^as 
 urenient and analysis of the inspired and expired air, and the deter- 
 mination of the respiratory (piotient. In several instances the last two 
 foims have been combined, ('alorimeters have also been devised by 
 many investigators. These have usually been combined with respira- 
 tion apparatus of some form. 
 
 ' U. 8. Dept. Agr., (Jllicc of Experiment fcitutions liiil. 45. 
 
10 
 
 An excellent summary of the methods and results of respiration 
 experiments up to about the year 1882, with descriptions of the apparatus 
 employed, has been prepared by Zuntz.^ About the same time a like 
 excellent account of inquiries regarding the income and outgo of heat 
 of the body was published by Eosenthal.^ Since that time numerous 
 forms of apparatus have been devised and a large number of experi- 
 ments have been carried out. Keports of these are published in the 
 various scientific journals and have, so far as known, not yet been 
 summarized. 
 
 The apparatus which was used in the present experiments differs in 
 its essential points from that used by other investigators. It consists 
 of a respiration apparatus similar in principle to that of Pettenkofer 
 and Voit,^ which belongs to the second class mentioned above. In 
 addition there are devices for the measurement of the energy liberated 
 by the organism. 
 
 Tor measuring and analyzing the incoming and outgoing air, new 
 methods have been devised, or the methods already in use have been 
 materially modified. The apparatus for measuring the outgo of energy 
 is entirely original. Therefore, though the apparatus resembles in 
 outward form the respiration apparatus of Pettenkofer and Voit, it dif- 
 fers in so many essential points that it may be fairly termed a new 
 form, and to it the name respiration calorimeter has been applied. 
 
 In the earlier experiments referred to above the subject remained in 
 the apparatus for short x>eriods, usually not more than twenty-four 
 hours. In the presen't experiments the subject remained for several 
 days inside the respiration chamber. 
 
 THE EXPERIMENTS REPORTED IN THIS BULLETIN. 
 
 The purpose of the present article is to give a description of the 
 apparatus used and of the methods which have been elaborated, 
 together with an account of the experiments thus far made by the 
 authors which bear directly upon the metabolism of matter. Four 
 experiments with men in which the metabolism of nitrogen and carbon 
 has been measured are described. The results obtained regarding the 
 metabolism of hydrogen and energy are to be withheld until some 
 changes which experience has indicated to be desirable in the appa- 
 ratus and methods can be made, and the results already obtained can 
 be verified and new ones added. 
 
 The four experiments, designated by the laboratory numbers 1, 2, 3, 
 and 4, were as follows : 
 
 No. 1. An experiment of fifty-four hours with a laboratory assistant. 
 
 No. 2. An experiment of fifty-four hours with a laboratory assistant. 
 
 'Hermann's Handbuch der Physiologie, vol. 4, pt. 2, pp. 86-162. 
 ^Handbuch der Physiologie, vol. i, pt. 2, pp. 289-456. 
 
 ^Pettenkofer and Volt's apparatus and a number of experiments made with it are 
 described in U. S. Dept. Agr., Of6ce of Esperinieut Stations Bui. 21, pp. 106-112. 
 
11 
 
 No. 3. An experiment of five days with a clieraist. 
 iSTo. 4. An experiment of twelve days with a physicist. 
 Several previous experiments, which were less complete, are not 
 reported here. 
 
 APPARATUS. 
 
 The first requisite for metabolism experiments of the kind here 
 reported is of course reliable methods and apparatus for the accurate 
 determination of the different ftictors of income and outgo during a 
 given period. This subject received much painstaking thought and 
 care in the present investigation. The fact, however, should be empha- 
 sized that although these experiments were carried out with much 
 attention to detail and accuracy, they are regarded simply as prelim- 
 inary to more elaborate, comprehensive, and exact investigations with 
 improved apparatus. 
 
 Fid. 1.— Ucsiiiration ciiliDiiiictor. 
 
 The apparatus used in tlie experiments herewith reported consists 
 es.srnf ially of a resi)irafion clianib(>r in wliich the subject stays daring 
 th<; cxperiinent, appliances for maintaining a current of air through 
 the respiration cliainbcr for ventilation, api)aiatns for measuring and 
 iinalyzing this ventilating cuirent of air, and ajjpliances for measnring 
 the heat given off from the body (see fig. 1). 
 
 Th(i appiiratns and methods for tln^ measurement of the heat given 
 off from the body, which were d«;vised by Piof. I*:. r>. K'osa, are lu'lieved 
 to be (piite novel. The experience gained in the, ns<', of these ai>plianc(^s 
 
12 
 
 has naturally suggested improvements in the details. The description 
 of this part of the apparatus is reserved for publication after the inves- 
 tigations have further progressed. 
 
 The room in which the apparatus is situated and in which the larger 
 part of the work of the experiment is carried on is in the basement 
 of the Orange Judd Hall of Natural Science and is a part of the chem- 
 ical laboratory of Wesleyan University. It is 35^ feet long, 20 feet 
 wide, and 9 feet high; well ventilated; supplied with gas, water, and 
 electricity, and heated by steam. During the period of the experi- 
 ments, which was in late winter, the steam heat was insufficient for 
 comfort during part of the night and gas stoves were used in addition. 
 As the building is of sandstone, with very heavy walls, the fluctuations 
 of temperature within, especially in the basement, are comparatively 
 slow. Light is su])plied by five large windows, and by gas and elec- 
 tricity. A Vj kilowatt motor, connected \\ith convenient shafting, fur- 
 nishes the power. 
 
 Opening out of this room is a smaller one, 5 by 11^ feet, fitted with 
 arrangements for cooking the food. It also serves as a dressing room 
 for the snbject at the times of entering and leaving the resijiratiou 
 chamber. 
 
 THE RESPIRATION CHAMBER. 
 
 The respiration chamber is a room or box in wliich a man may live 
 comfortably during the period of an experiment. The inside dimen- 
 sions are: Length, 2.15 meters; width, 1.22 meters; height, 1 .92 meters. 
 It is provided with conveniences for sitting, sleeping, eating, and 
 working, as well as arrangements for ventilation and for the study of 
 the respiratory products. The chamber consists, in fact, of three con- 
 centric boxes, the inner one of metal and the two outer ones of wood. 
 
 The inner box, of which the inside dimensions have just been given, 
 is donble walled, the inner wall being of sheet copper, the outer of 
 sheet zinc. The two walls are 8 centimeters apart. This double-walled 
 box is held in shape by a wooden framework between the two metal 
 walls. The four vertical corners are rounded, as this simplifies the 
 construction and makes tlie apparatus rather more convenient for use. 
 The inside volume is approximately 4.8 cubic meters (see figs. 2 and 3). 
 
 An opening in the front' end of the metal chamber, 70 centimeters 
 high and 49 centimeters wide, serves both the purpose of a window 
 and a door for entrance and exit. Considerable dilficulty was experi 
 enced in securing an air-tight closure for this door. After numerous 
 unsuccessful experiments with frames of wood and metal and with India 
 rubber gaskets and other appliances, the simpler plan was adopted of 
 using a large pane of glass in a frame as is done in ordinary windows 
 
 1 In these descriptions the end in which the window is situated is called the front. 
 The terms right aiul left are applied to the sides nt the right and left of a person 
 standing outside at the front end and faciuji- the window. 
 
13 
 
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14 
 
 and securing it with putty. The hxbor of putting the glass in at the 
 beginning and taking it out at the end of an experiment is very small, 
 and the plan serves the purpose admirably. 
 
 Outside of this double- walled metal box are casings of wood. The 
 outer wooden walls are supplied with glass doors turning on hinges 
 and facing the doors in the metal box. 
 
 The jnirpose of the double metal Avail of the inner chamber and of 
 tlie wooden casings is to facilitate the use of the devices for measure 
 ments of heat. The chief use of these latter devices is in connection 
 witli the experiments to determine the income and outgo of energy, 
 which are not yet complete for publication. 
 
 Numerous passages through the walls are needed for tubes, to convey 
 the ventilating current of air and for a current of water to carry off the 
 heat generated by the body of the occupant of the chamber, wires for 
 various electric connections, metal rods for certain connections between 
 the interior and exterior apparatus, and, finally, the "food tube" for 
 passing the food and drink into the apparatus and taking out the solid 
 and liquid excretory products. The tubes referred to are of various 
 sizes and made of either brass or copper. The "ventilating tubes" 
 have an internal diameter of 4 centimeters. The food aperture is of 
 copper and has an internal diameter of 15 centimeters. It is situated 
 on the left side of the apparatus, and is provided with a cap at each 
 end. The outer cap is attached by a screw so that it may be made air- 
 tight. In putting in the food and other materials the cap is taken off", 
 the receptacle containing the food is placed in the tube and the cap put 
 on again. A signal is then given to the man inside who removes the 
 inner cap and takes out the receptacle. The materials from within are 
 passed out in corresponding manner. In this way there is no danger 
 of ingress or egress of any considerable quantity of air. 
 
 A telephone furnishes a means of communication between the inside 
 and outside of the chamber; the wires of the telephone pass through 
 rubber stoppers inserted, in a tube, which, in its turn, passes through 
 all of the boxes and walls and is soldered to the inner copper wall. 
 Other wires through the same tube provide for electrical connection 
 with a small bell on the outside so that the i^erson within may call an 
 attendant whenever desired. 
 
 Adequate provision is made for the ventilation of the chamber and 
 for maintaining a uniform humidity and temperature by means of the 
 appliances described below (p. 16). An inconvenient rise of tempera- 
 ture is prevented by a current of cold water which passes through a 
 system of pipes inside of the chamber. This device forms a part of 
 the arrangements for measuring the heat given off" from the body. As 
 the results of such measurements are not reported in this article, it will 
 suffice to say that the plan followed is in fact the opposite of that used 
 in heating houses by hot water radiators, i. e., instead of passing hot 
 
15 
 
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16 
 
 water tliiougli radiators to give off heat for warming the air, cold water 
 is passed through absorbers to remove heat from the air. 
 
 A wet and dry bulb hygrometer, capable of being read to tenths of 
 a degree centigrade, is hung in the rear of the chamber and observa- 
 tions w^ere made by the occupant, generally at intervals of two hours, 
 during the period of the experiment. These observations were reported 
 by the telephone and show the hygrometric condition of the air inside 
 of the apparatus. 
 
 The furniture used in the experiments consisted of a light folding 
 canvas cot bed, a folding chair, and a folding table. Such clothing and 
 bedding as were needed for comfort Avere taken in by the man at the 
 beginning of the experiment, and small articles were passed in and out 
 through the food tube at convenient times. Tlie floor was protected by 
 carpeting. The amounts of water held by the furniture and clothing, 
 etc., were determined as accurately as practicable by weighings at the 
 beginning and end of each experiment. 
 
 The arrangements for measuring and sampling the air are described 
 as they were actually used iu the experiments. They have since been 
 replac ed by others which will be described with accounts of experi- 
 ments now in i^rogress. 
 
 APPLIANCES FOR VENTILATION AND FOR THE MKASUREMENT AND 
 ANALYSIS OF THE VENTILATING CURRENT OF AIR. 
 
 A satisfactory respiration experiment involves the maintenance of a 
 proper current of air, the accurate measurement of its volume, and the 
 determination of the respiratory products. When a living subject is 
 in the respiration chamber and breathes its air it is essential that the 
 ventilation be sufficient for his comfort, but it is important that the 
 amount passed through the chamber be not too large, on account of 
 the difliculty of accurate measurement and analysis. With a small 
 current the reasonably accurate measurement of the volume is easier 
 than with a large one, smaller samples are needed for analysis, and the 
 samples can be taken and the analyses made more accurately. 
 
 It is evident that the greatest care is needed to devise such mechan- 
 ism and methods as will secure the maximum at-curacy of measurement 
 and sampling of the air and of determination of the respiratory prod- 
 ucts. In the large amount of work done during the last thirty years 
 with various modiiicatious of the Pettenkofer apparatus the chief diffi- 
 culties have been iu the measurement of the air and determinations of 
 the water. The method generally followed has been to measure both 
 the total volume of air and the volume of the samples by gas meters, 
 and to use the samples for determining the carbon dioxid and water by 
 absorption and the marsh gas and other volatile organic comi^ounds 
 by combustion. 
 
 The same general method has been followed in these experiments. 
 The air was drawn through the apparatus by means of si^ecially devised 
 
17 
 
 jiir i)iiini)s, and its total vuluiue measured by ii gas meter especially 
 constructed for the i)urpose. The samples of incoming and outgoing air 
 were drawn by means of aspirators, the carbon dioxid in the sample 
 was determined by absorption by soda lime, and the water by absorp- 
 tion by sulpliuric acid. 
 
 As the air was drawn and not forced through the apparatus, and 
 especial pains were taken to make both the respiration chamber and 
 the connecting pipes as nearly air-tight as possible, it was believed 
 that the air which passed through the meter and was measured by it 
 represented very accurately that wliich had passed through the cham- 
 ber and received the juodncts of respiration. It is not certain that the 
 chamber was absolutely air-tight, but at no place could any current of 
 incoming air other than that passing through the entrance and exit 
 tubes be found sufficient to affect the ilamc of a candle. Indeed, it was 
 hardly ex]K'cte(l that any considerable <|uaiitity of air could enter or 
 pass out in any other way even if the chamber had not Ijeen tight, since 
 
 Fli;. t. — Oiitliiii' .skclrli of icsiiiratidii ;i]i])ar;i(ii.s. 
 
 the tension within the chamber was very slight, the barometric pres- 
 sure differing from that of the outside air by only a fraction of a milli- 
 meter of mercury. The volume of air passing through the apparatus 
 varied from 50 to 1~> liters jx'r minute. The longest experiment was of 
 twelve days' duration, and was made with an air current of approxi- 
 mately 55 liters per minute. 
 
 It is desiralde to have the incoming current of air as dry as i)ossible, 
 as stated above. The smaller and more uniform the amounts of water 
 the easier and more accurate are the analytical deteniiinations, and, 
 birtheiiuore, the amount of ventilation needed for the comfort of the 
 ofcnpant of the (jhamber is less with little than with much moisture. 
 To redu<;e tin; amount to aininimum the air which caitiC from out of 
 doorB was dried before it entered the chamber. This drying was easily 
 accomplished by surrounding a portion of tin; pi[)e through which it 
 passed with a freezing mixture of salt and ice. 
 U771_]So. 11 2 
 
18 
 
 The course of the air in its passage from outside through the diiferent 
 parts of the apparatus to the pumps was as follows (see fig. 4) : It entered 
 through a window by a pipe of 7.5 centimeters internal diameter and 
 was drawn through a freezer (Ej) consisting of a system of 10-centimeter 
 copper pipes packed in ice and salt; thence it was again conveyed by the 
 7.5 centimeter air pipe (Dj) to the smaller air pipe which passes through 
 the front wall of the apparatus at the right of the window (B) and about 
 1.2 meters from the bottom of the chamber (A). In its passage from the 
 freezer to the chamber it was warmed so that it entered the latter at 
 the desired temperature. The warming was done by a 16 candlepower 
 incandescent electric lamp placed inside the air pipe. In this way the 
 temperature of the entering current of air was easily regulated. The 
 air entering the chamber makes a direct downward turn through a cop- 
 per pipe 10 centimeters in diameter which opens into the lower right- 
 hand front corner of the chamber. Tlie outgoing air is drawn from the 
 upper left-hand corner of the rear end of the chamber, i. e,, from a point 
 diagonally opposite that at whicli the incoming air is delivered. It is 
 conveyed from the latter i^oint by a lO-centimeter copper tube along 
 the top of the chamber to tlie front end and then downward to the 
 copper tube (1)2) through which it passes out. In this way a favorable 
 distribution of the air in the chamber is obtained. Tlie diameter of the 
 brass tubes has proven ample for the uninterrui:)ted passage of such 
 currents of air as liave been found desirable for the experiment. On 
 coming out of the chamber the ventilating current of air was passed 
 through another freezing apparatus (E2) by which the larger part of the 
 moisture was collected. Thence it passed through the meter (F) by 
 which its volume was measured and onward to the air pump (H). Since, 
 however, the action of the pump would vary the tension, a tension 
 equalizer (G) was placed between the pump and the meter. 
 
 Samples of the incoming air were taken from the entrance pipe just 
 as it entered the chamber. Samples of the outgoing air were likewise 
 taken from the exit pipes just as it entered the meter. 
 
 The several parts of this apparatus for maintenance and meas.uring 
 the current of air may be described in more detail as follows : 
 
 Two piston pumps were used for drawing the air tbrough the appa- 
 ratus. They were so arranged that either could be used alone for a 
 smaller current, or the two together for a larger current. In most of 
 the experiments here described, however, only one pump was used. 
 The piston of each pump was moved in a brass cylinder by cranks at 
 the end of a shaft, so that each pump made a double stroke for each 
 revolution of the shaft. This shaft was belted to the main shaft, which 
 works directly from the motor, and runs at the rate of about 300 revolu- 
 tions per minute. The connections were such that the pump made in 
 general about 75 strokes per minute. The strokes were recorded by an 
 
19 
 
 ordinary autouiatic register reading to 100,000. As the volume of air 
 l»er stroke was known approxinuitely this record made a rough check 
 upon the uieasureinents with the meter. Desirabh; changes in the rate 
 of How of air thiough the puni}) are effected by varying the length of 
 tlic stroke. tUe devices for this i)urpose being such that the desired 
 clianges could be made with ease and accuracy. When one of the 
 pumps drew Co liters per miuute each stroke represented approximately 
 0.7 liter. 
 
 TKNSION Ei^l ALIZEK. 
 
 When the [luiiips were connected directly with the meter the motion 
 of the latter was intermittent on account of the variations in air pres- 
 sure with each stroke of the ]»uinp. To reduce these variations of 
 tension to a minimum and make the i)ressare of the air as it passed 
 through Ihe meter more unitbrm a device was employed to which the 
 name tension equalizer was given. This was placed so that the air 
 passed through it in going from the meter to tlie pump. It consists of 
 a cylinder about 50 centimeters high and 40 centimeters in diameter. 
 The sides and bottom of this are of tin plate. Over the top a piece of 
 rubl)er sheeting, such as is used by dentists, is loosely stretched and 
 tightly bound. Although its capacity is only between 50 and 00 liters, 
 yet the action of the rubber top was such that the variation in pressure 
 of the meter as measured by a water column amounted to only a few 
 millimeters, and no irregularity could be seen in the motion of the 
 index ou the meter. 
 
 METE II EOK MEASURING AIR. 
 
 The meter' was of the kind employed by Professor Zuntz, of the 
 Agricultural Institute of the University of Berlin, in his respiration 
 exi)eriments with horses, dogs, and other animals, and with man. Pro- 
 fessor Zuntz was so kind as not only to assist in getting the meter, but 
 also to test it in his laboratory. The apparatus has been brietiy 
 described by Professor Zunt/.,'- and only the essential features will be 
 noticed here. 
 
 The readings of the nu;ter are indicated by hands revolving on a 
 large dial and recording to 10,000 liters. In the experiments the meter 
 is read for the number of thousands of liters, while the numbers often 
 thousands of liters were checked by the register above referred to 
 uinler the head of "Air pump" (]>. 18). 
 
 The accuiacy of measurements of volumes of air by a gas meter has 
 l)ecn a subject of much discussion aud no little experimenting, and the 
 attention given to it in this laboratory has been not inconsiderable. 
 The errors involved are undoubtedly small, and with care may, it is 
 believed, be reduced to a very small fraction of the total volume of air 
 to be measured. 
 
 'Maili- by S. KlHt.r, <if ]{. rlin. 
 
 ■"Liindw. .Jiihrb., IS (ISSO;, p. 1; :i1h<) l''lii;,';L,'o, llygii;iii,s(lic lJiit.i8U(luiii<,'8- 
 mi;tlio<leii, p. DiJl. 
 
20 
 
 In using the meter a thermometer was inserted at one side, so that 
 its bulb was immersed in the water within the meter and its readings 
 were taken as indicating the temperature of the water. This was 
 assumed to be also the temperature of the air as it left the water. The 
 air was assumed to be saturated with aqueous vapor at that temjjera- 
 ture. As the air passed through at the slow rate of from 55 to 80 liters 
 per minute, it was not believed that this assumption involved a very 
 large error. It was believed, however, tliat means (tould be found by 
 which the errors of measurement could be materially reduced. An 
 apparatus for the purpose has been devised and made by Mr. O. S. 
 Blakeslee, and the preliminary observations made with it are quite sat- 
 isfactory. It is practically a large mercury pump, so arranged as to 
 serve the double purpose of maintaining the current of air and deliver- 
 ing aliquot samples for analysis. 
 
 ASPIRATORS FOR SAMPLING AIR. 
 
 The samples of air for analysis were drawn by means of aspirators (I). 
 These aspirators, three in number, are cylinders of galvanized iron, 
 standing upright, with conical ends. The cylinders are 50 centimeters 
 in diameter and 40 centimeters in height, exclusive of the cones which 
 form the ends. The cones are approximately 8 centimeters in height, 
 making the whole length of the cylinder, from apex to apex, about 02 
 centimeters. At the apex of each cone is a short neck of brass tubing. 
 Horizontal tubes connect the two necks with an upright glass tube ou 
 the side of the asi)irator. This serves as a gauge and shows the height 
 of the water. It is accurately marked at the top and bottom, and thus 
 permits the drawing off of a detinit(i quantity of water and consequently 
 the accurate measurement of the volume. The aspirators are sustained 
 in a framework and set in cement to give them hrm support. At the top 
 of each is a 3-way valve, Avhich serves to make connections with the 
 tubes (Ki and IC,) bringing the samples of air. A manometer indicates the 
 tension and a thermometer the temperature of the air in the as[)irators. 
 Here again the air was assumed in the experiments to be saturated at 
 tlie temperature indicated by the thermometer. The volume of water 
 or air held by each of these aspirators was determined by weighing the 
 water which it held, and was from 150 to 103 liters. The connection 
 between the aspirators aud the tubes, through which the main current 
 of air passes, was made by 0-ceutimeter brass tubes. The sample cur- 
 rents of air are brought from the main air current through these small 
 brass tubes into the apparatus for the absorption of carbon dioxid and 
 water (Li and La) and then into the aspirators, by which the samples 
 are drawn and the volume of each sample is measured. 
 
 The rate of iiow is regulated in a very simple manner. The water 
 passes out from the bottom of the aspirators through a short brass 
 tube which is connected with a longer rubber tube. Thelast is provided 
 with a screw pinchcock and a metallic nozzle at the lower end, which 
 
21 
 
 is riised or lowered at will, thus vaiyiiiji the head of water. In tak- 
 ing; a sample, the aspirator is first filled to the mark indicated on the 
 winter gauge outside. The connection is made by the 3 way cock with 
 the tube through which the sample of air is drawn from the main cur- 
 rent. The flow of water from the bottom is started with the nozzle at 
 the end of the rubber tube at the height of about 1 meter from the floor. 
 The water which first comes out is collected in a graduated cylinder. 
 The amount in one minute shows the rate of flow. If this is too fast or 
 too slow, it is changed by means of the pinchcock on the rubber tube. 
 AVhen the i)roi)er flow is established, ordinarily about 500 or (iOO cubic 
 centimeters per minute, it is allowed to proceed. As the water level in 
 the aspirator falls, the nozzle is lowered and the rate of flow is observed 
 at intervals, generally of about one half hour. In this way it is easy to 
 make the rate rapid or slow at discretion and reasonably uniform. 
 
 AITARATUS FOR DETERMINING CARBON DIOXID AND WATER IN SAMPLES OF AIR. 
 
 The constituents of the air determined in the experiments described 
 beyond were carbon dioxid and aqueons vapor, although only the for- 
 mer is reported. The device above referred to (p. 17) for removing the 
 moisture from the main air current by cooling to about — 17° C. leaves a 
 small and fairly uniform amount of moisture, and thus greatly facili- 
 tates the determination of the latter in the sam])les analyzed. Four 
 U -tubes are used for the analysis, two, filled with soda-lime, for the 
 carbon dioxid, and two, containing sulphuric acid, for the water of each 
 saniple. For weighing they are hung by loops of platinum or aluminum 
 wire. 
 
 Freezing apparatun. — It was found very desirable in these experi- 
 ments to have the air enter the respiration chamber as dry as possible. 
 It was with this fa(;t in view that the ])lan was first adoi>ted for freez- 
 ing the air before it entered the chamber. The freezer used for this 
 purpose consists practically of two large U -tubes of copper. These are 
 (;onnected with each other and with the i)iiie through which the current 
 of incoming air lh)ws. They stand upright in a wooden box which is 
 ke])t filled with a freezing mixture of salt and ice. Fach of the four 
 ui)rights of the two U-tubes consists of a pipe made of (No. 1(5) sheet 
 (•o])per, 10 ccntinieters in diameter and 01.4 centimeters in length. 
 These ui)right pipes are so connected by horizontal elbows that the 
 whole forms a compact mass 1 meter in length and a little over L'O cen- 
 timeters s(|uare. In this way the current of air has to ]>ass through 
 neaily '.'>Mr> meters of cojjper tubing which is covered by the i'wv/Aug 
 mixture. To still further increase the cooling surface of metal, and 
 with it the rapidity of tlu; ])assage of heat from the air to the freezing 
 niixtuH', a number of vanes of she<;( eopix'i' are jthiced inside the lour 
 lengths of copper tubing. lOach vane is parallel with the axis of the 
 tube and is soldered to the side so as to |)roJect .'{.8 centimet(!rs toward 
 tlie (tenter in a radial direction. In tlu'. horizontal elbow througli wiiich 
 tlie air, after lia\ing jtassed through (he lour tubes, returns to the main 
 
22 
 
 conducting pipe is an orifice in which is inserted a thermometer. This 
 indicated the temperature of the air as it left the freezer, under ordinary 
 conditions to be from about — 17° to — 18° 0. The wooden box which 
 held the freezing mixture and the freezing apparatus had at the bottom 
 an outlet for the brine. The ice was finely crushed, mixed with salt, 
 and packed closely between the freezer and the box. 
 
 When the experiment was continued for twelve days, the moisture 
 which gathered in the form of frost on the inside of the freezing appa- 
 ratus accumulated so as to retard the passage of the current. Accord- 
 ingly the pump was stopped in the middle of the experiment, the 
 freezer taken out, and hot water poured upon it so as to melt the ice 
 inside. It was then emptied, put back in place, and repacked in the 
 freezing mixture. The whole operation did not last more than twenty 
 minutes. The stoppage of the current of air during this time did not 
 cause the least discomfort to the person inside the chamber. Indeed, 
 he was not aware of it until he was told. 
 
 It was found necessary to repack the space outside the freezer with 
 ice and salt about once in two hours under ordinary conditions. This 
 method of removing the excess of moisture from the air before it enters 
 the chamber proved so satisfactory as to lead to its adoption in quanti- 
 tative determinations of the moisture in the outgoing air. For this 
 purpose, however, a somewhat more complicated freezer is necessitated 
 by the fact that the water which it collects must be accurately weighed. 
 The detailed description of this freezer is reserved for future publi- 
 cation. 
 
 Objections to the use of ice and salt for freezing are the trouble of 
 frequent renewal, the expense for material and labor, which was not 
 inconsiderable, the difficulty of getting a satisfactory low temperature, 
 and especially the impossibility of maintaining a constant tempera- 
 ture. For the later experiments immersing the freezers in brine cooled 
 by the expansion of ammonia gas has been adopted.^ 
 
 METHODS OF SAMPLING AND ANALYSIS. 
 ANALYSIS OF FOOD, FECES, AND UEINE. 
 
 The methods of analysis used were essentially those adopted by the 
 Association of Oificial Agricultural Chemists, with such modifications 
 as exx)erience and circumstances have shown to be desirable.^ 
 
 PREPARATION AND SAMPLING OF FOOD. 
 
 In the preparation of the food special effort was made to secure such 
 mechanical condition of the materials as would facilitate the most 
 thorough and accurate sampling, The samples, when too moist for 
 
 1 The so-called "Economical Ice Machine," made by the Atlantic Refrigerating 
 Comjiauy, of Springfield, Mass., has been found very satisfactory for this purpose. 
 
 2 For detailed descriptions of the usual methods followed, with the possible sources 
 of error involved, see U. S. Dept. Agr., Division of Chemistry Bui. 46; Office of 
 Experiment Stations Buls. 21, pp. 39-52, and 29, pp. 8,9. 
 
23 
 
 griiuliiig", were partially dried: tlie material in the original or partially 
 dried form was sampled and ground, first in an ordinary "Excelsior 
 mill," afterwards in a Maercker-Dreefs mill, by Avlii(;li it is easily 
 reduced to a very line powder. Some materials, containing consider- 
 able quantities of fat or sugars, are not easily groujid in this way. 
 Meats, eggs, and canned pears, for instance, were rubbed in a mortar 
 until they wei-e homogeneous. The ground material was preserved for 
 analysis in Tightly sto])i)ered bottles. It lias been found, however, that 
 when such materials are keiit in bottles closed with glass, or even rub- 
 ber stoppers, they are apt to change in moisture content on long stand- 
 ing. Unless the analyses are to be made immediately, or within three 
 or four days at longest, it is best to seal glass-stoppered bottles with 
 parartin. Even then, if the material has stood for some weeks, it will 
 sometimes be found desirable to repeat the determinations of moisture. 
 When nearly all the water is removed from the materials, as is done in 
 the process of partial drying referred to beyond (p. 24), no indications 
 of decomposition, even of meats, Avere found for some weeks or months. 
 It is, however, noticeable that when the samples of meats containing 
 more or less fat are thus dried and finely ground, and are allowed to 
 stand in the working room of the laboratory, the fat gradually sepa- 
 rates ami settles to the bottom of the bottle. This is an indication of 
 the need of careful mixing of such materials Just before the weighing 
 of portions for analysis. 
 
 Some food materials, however, are so dry as not to require the partial 
 drying. Ordinary fine wheat Hour is ready for analysis at once, or can 
 be preserved for some time in tightly closed bottles. The coarser tlours 
 and meals, rice, and common crackers and biscuit can generally be 
 ground and kept for analysis without drying. 
 
 Since in some instancies the treatment was somewhat detailed, the 
 methods used for the ])reparation of each kind of food for analysis may 
 be brieriy outlined. 
 
 />V(9/'. — A lean i)iece of round steak was selected and the superfluous 
 fat w.as carefully removed. The meat was then cut in long strips and 
 rnn thiongh a meat chopper several times, thus securing fine division 
 and thoiough mixture. Aftei' leaving the chopper it was weighed out 
 in balls or cakes of O'J.l grams each, and ]>la(;ed on a plate covered with 
 a glass cover. When meat was cooked for a meal three of these balls 
 were cooked at the same time and in the same dish; two of them were 
 eaten, and tlie thir<l served as a sampl(^ for analysis. 
 
 Ihuad. — Tiiiee kinds were used, "white bread," made of fine wheat 
 Hour; "brown bread," of wheat and rye flour and corn meal; and rye 
 bread. To insure like composition and lik;> proportions of crust and 
 ciiiinb, the loaf was cn( in slices and alternate slices wer(^ taken for 
 eating and analysis. 
 
 Oatmeal. — One of the (;ommon commercial pieparations of oatmeal 
 was used. A cei'tain weight of the dry material was cooked in water. 
 Ah there was no reason to fcai' h)ss of material the composition of the 
 
24 
 
 oatmeal as eaten was assumed from that of the original material, tak- 
 ing- into account tlie water added in cooking. 
 
 Potatoes. — These were boiled with the skins on. After pouring off 
 the water the skins were removed and the potatoes put through a ])otato 
 maslier. The portion to be eaten was weighed, a sample of like weight 
 being taken at the same time for analysis. 
 
 Apples. — The fresh fruit was pared. ai5d the cores removed, notliing 
 but the apple pulp being eaten by the subject. Samples of the pulp 
 were analyzed. 
 
 Canned heans^ pears., and peaches. — Tiiese three materials wore served 
 cold, and required no special preparation. Samples from the different 
 cans were used for analysis. 
 
 Milli craclcers, sugar, and, cheese. — These were served as purchased in 
 the market, without any special preparation. Samples of each lot were 
 analyzed. 
 
 Uggs. — Eggs of approximately the same weight were selected. Three 
 were boiled in the same dish of water, two were eaten, and one was 
 taken as a samjile. 
 
 Butter. — This was a creainery butter as purcliased. No partial dry- 
 ing- was necessary. Samples were taken at each meal, each sample 
 being of the same weight as the portion eaten. 
 
 Milk. — Aliquot portions Avere taken from the milk of each day. 
 These samples were preserved until analyzed by addition of potassium 
 bichromate. 
 
 As fast as samjiles were taken they were either immediately '^ partially 
 dried," as in the case of meat, bread, potatoes, etc., or preserved for future 
 analysis by some antiseptic, such as potassium bichromate, as in the case 
 of milk. The several samples of a g-iven material for a. given period were 
 joined together and resampled, so that a single analysis served for the 
 whole of that special lot. Thus the several samples of "white" bread 
 for a given number of days were united, and after the partial drying 
 were well mixed and a single sample representing the whole was 
 analyzed. This course was followed with the other materials in so far 
 as it was feasible without risk of inaccuracy. 
 
 Partial drying. — For this process portions of 50 grams each were 
 placed in shallow porcelain sauce dishes and heated in a large air bath 
 at the usual temperature of 90° 0. or thereabouts for a period of thirty- 
 six hours. They were then placed on a shelf lightly covered with paper, 
 and thus exposed to the air in the laboratory for twenty-four hours. 
 At the end of this time the moisture content had become practically 
 constant and the samples were weighed and the loss of moisture noted. 
 They were then ground, placed in properly marked bottles, and set 
 aside for analysis. 
 
 Complete drying.— For the determination of water- free substance the 
 usual methods were employed. The time of drying was usually five 
 
25 
 
 lionrs. ill accordance with the official methods. This, however, did not 
 suffice ill all cases, and longer heating was necessary. It is well 
 known that one of the most difficult operations in the laboratory is the 
 accurate determination of moisture in animal and vegetable substances, 
 and not a little work has been done in this laboratory with a view to 
 improving the accuracy of moisture determinations.' 
 
 !■■ AT — ETIl K R K X T RA CT. 
 
 Tlie sample which had been dried in hydrogen for the water determi- 
 nation was used for the determination of crude fat. To this end it was 
 extracted in the usual way with ether, which had been digested with 
 fused calcium chlorid and distilled over that substance. Continuous 
 extraction for sixteen hours was generally sufficient. 
 
 For determination of ash the material was incinerated in tlie follow- 
 ing manner: The mass was tirst charred in a platinum capsule and 
 then extracted with hot distilled water, the insoluble matter being 
 collected on a filter; the filter with its contents was then returned to 
 the i)latinum capsule and the whole heated until the incineration was 
 conii)lete. The aqueous extract was added, and after eva]>oration the 
 whole residue was heated at low redness until the ash was white. 
 
 N1T1!< XiKN — PROTEIN. 
 
 Nitrogen was determined by the Kjeldahl method, tlie amount of 
 nitrogen thus found multiplied by 0,25 being taken as representing the 
 protein. As the proportion of nitrogen is the basis of the calculations 
 of nitrogen bahiuce, the method of estimating juoteiu by difierences, 
 whidi is often followed in analysis of meats and other materials c(m- 
 taining little or no carbohydrates and which is doubtless often more 
 accurate, would not be in jilace here. 
 
 Kxi)erience in this la])oratory with meats and other animal tissues 
 confirms tlie observations of other chemists that there is great danger 
 of incompletes ammonification of the nitrogen in these substances when 
 treated with sidphuric acid ami other reagents as ordinarily lecom- 
 mended in tlieKj(ddahl process. Jt appearsthnl minierous albnniinoid 
 substances resist <le(;omposition, or at any rate the comi)lete union of 
 nitrogen and hydrogen to form ammonia. With such substaiu-es it was 
 found necessary to continue the digestion for some time after the sul- 
 plinric acid solution had Ixniome coloiless. 'J'he clearness of the solu- 
 tion was by no nu'.ans an indication of complete ammonification. The 
 pnxtess has frequently been found to be incomplete when the digestion 
 liad been continued for an hour or ev<!n two hours after the disappear- 
 ance of color. It is safer to continue the digesti(»n for tliree or four 
 iiours a,rter tlie solution lisis become elecolorized. 
 
 Se*', II. S. I).-])t. A«r., OClicr of i:\|..|iiiirlit, SI:itiuiiH I'.iil. 'J I , ].. II. 
 
26 
 
 Casein. — In analysis of butter the casein was determined directly. 
 The butter was placed in a Groocli crucible and the fat dissolved out 
 with ether. The casein and mineral matters were weighed together and 
 the casein burned. The loss in weight on burning was taken as repre- 
 senting the casein. The danger of slight error here on account of the 
 presence of milk sugar is a subject which has not been investigated. 
 
 CARBON AND HYDROGEN. 
 
 The food materials, feces, and dried urine were burned with cupric 
 oxid with the aid of a current of oxygen, in accordance with the usual 
 methods. The carbon dioxid was absorbed by potassium hydroxid and 
 the water by concentrated sulphuric acid.' 
 
 HEATS OP COMBUSTION— FUEL VALUES. 
 
 The determinations of heats of combustion of food materials, feces, 
 and dried residue of urine were made with the bomb calorimeter, as 
 described in previous publications.^ The apparatus and method 
 have been in use in this laboratory for the i)ast three years, and have 
 been found very satisfactory. 
 
 COLLECTING, PI'.ESERVING, AND SAJIPLING OF FECES AND URINE. 
 
 In the digestion experiments (which began before the subject entered 
 the respiration chamber, as explained beyond) it was necessary that 
 the feces of a given diet should be separated from those of the diet 
 immediately preceding. To effect a sharp separation the subject had a 
 supper of bread and milk, at which time he took six or seven large gel- 
 atin ciipsules containing Iam])black.-' The following morning the diet 
 decided upon for the digestion experiment was begun and strictly 
 adhered to throughout the whole exi)eriment. Tlie sampling of food 
 for analysis was also begun at this first meal. On the second or third 
 day the milk feces, having a characteristic consistency and colored with 
 lampblack, generally appeared. When there was no indication of 
 diarrhea, the separation of the residues from the two different kinds of 
 food may be considered reasonably accurate inasmuch as the portion 
 from the meal of bread and milk is easily distinguished from that of 
 the succeeding meal. All the feces following that of the bread and 
 milk were saved. At the end of the experiment a supper of bread and 
 milk with lampblack was again taken, and all the feces up to the 
 point where the milk residue apj^eared were considered as belonging 
 to the undigested residues of the diet under study. At first the feces 
 of each day during the experiment were separated, weighed, and in 
 
 iFor observations upon the sources of error in the ordinary methods of analysis of 
 animal and vegetable products, see IT. S. Dept. Agr., Office of Experiment Stations 
 Bill. 21, pp. 38-52. 
 
 -U. S. Dept. Agr., Office of Experiment .Stations 13nl. 21, pp. 123-126; Connecticut 
 Storrs Rta. Rpt. 1894, i)p. 135-157. 
 
 ^Later experience has shown that so nmcli lampblack is unnecessary. 
 
27 
 
 some cases separately analyzed also. This, however, proved unnec- 
 essary, as it was found that the composition with a given diet remained 
 very nearly the same from day to day. 
 
 The urine is obviously a very important tsictor as regards the metabo- 
 lism of nitrogen. Consequently its collection and preservation for 
 analysis require especial attention. Unfortunately it was ])ossiblo to 
 give only limited attention to the subject during these experiments. It 
 is believed that a more thorough investigation of the character and 
 constituents of urine in respiration experiments Mill prove of no little 
 physiological importance. 
 
 In these ex})eriments the bladder was emptied every morning at 
 o'clock. All the urine voided between that hour and the next morning 
 at the same hour was taken as the urine for that day. p]ach day's 
 urine was carefully weighed, thymol being added as a preserving agent. 
 
 The total nitrogen in the urine was determined in the fresh substance 
 by the Kjeldahl method. 
 
 For the determination of carbon and hydrogen the urine was dried 
 in a partial vacuum over sulpliuric acid. It was found by repeated 
 tests that drying urine by heat involves considerable loss of nitrogen. 
 The importance of avoiding this loss led to investigations which showed 
 that fresh urine could be dried in a vacuum over sulphuric acid with- 
 ont material loss of nitrogen. Accordingly it was assumed that there 
 would also be extremely' little loss of carbon and hydrogen, and the 
 substance thus dried was taken for the determinations of these ele- 
 iiicnts. The same method was followed, though generally with a some- 
 what longer period of drying, to determine the amount of water-free 
 substance. The percentage of water in this " partially dried hi r<(ciio^^ 
 urine was taken into account in calculating the percentage of carbon 
 as determined by combustion with cupric oxid. 
 
 ANALYSIS OF RESPIRATORY I'RODUOTS. 
 
 In ex]>eriments of the class to which those here rei)orted belong the 
 res|)iiatory produ<-ts commonly determined are carbon dioxid, water, 
 and volatile organic compounds. 
 
 CAItnf)X DIOXII). 
 
 The determination of carbon dioxid is most essential, and is, of course, 
 always attempted. The experience of a number of experimenters dur- 
 ing tlic past twenty-five years implies that the difficulties in the way of 
 fairly accurate results ar<' not insuj>erable. Tlie carbon dioxid given 
 oil" in respiration is quickly dilfused through the air and readily con- 
 veyed away by the ventilating cunent, so that the accurate measure- 
 ment of that current and dclennination of the jx-rcentage of carbon 
 <lioxid Hufliccs for the ordinary ))Ui|)i)S(',s of c^xjierimcnt. 
 
 For the al)8orption of carbon dioxiil soda-lime lias, in onr cxpciicnce, 
 jiroved tlic most siitislactory reagent. It must, howcAcr, lia\'e the 
 
28 
 
 proper proportions of soda, lime, aiul water to fit it for tbe purpose. 
 It may be made as follows : One kilogram of commercial caustic soda 
 is treated with 600 cubic centimeters of water, forming a very strong 
 solution, or rather a pasty mass. To this a kilogram of quicklime is 
 added. The latter is slaked by the water of the soda solution. The 
 mixture is rapidly stirred. ISTo heating is necessary. If there are any 
 lumps, they are broken into small pieces, and the soda-lime thus made 
 is immediately put into large bottles or fruit jars and tightly sealed. 
 
 The presence of a certain amount of moisture in the soda-lime is 
 essential to ttie complete absorption of the carbon dioxid. As the soda- 
 lime is converted into the carbonates of sodium and calcium the mass 
 whitens, and the advancement of this change in color from one end of 
 the column of soda-lime to the other is apparent as the absorption of 
 carbon dioxid proceeds. This affords a very good check on the effi- 
 ciency of the tube. In the preliminary tests of the method, as in the 
 actual determinations, two tubes were used in series, and after each 
 determination the second tube was moved toward the incoming current, 
 so tliat it became the first tube, and a fresh one was inserted to serve 
 as second tube. ISTumerous experiments were made with varying quan- 
 tities of carbon dioxid in the air and with varying rates of flow to see 
 if the system would thoroughly remove all carbon dioxid. A check 
 tube containing glass beads drenched with bnrium-hydroxid solution 
 failed to indicate the slightest trace of carbon dioxid, with 150 liters of 
 aspirated air, containing 3.5 grams of carbon dioxid, and running at 
 the rate of 500 cubic centimeters per minute. 
 
 The value of the soda lime as an absorbent for carbon dioxid was 
 further demonstrated bypassing a current of air previously freed from 
 carbon dioxid through a flask in which a known quantity of carbon 
 dioxid was generated from pure sodium carbonate or calcite. As the 
 air with this carbon dioxid came from the flask it was j)assed over sul- 
 phuric acid to absorb the water and then through two tubes containing 
 soda-lime, then through a tube with sulphuric acid to catch the water 
 set free from the soda-lime, and finally through a tube containing 
 barium hydroxid solution to detect any traces of carbon dioxid which 
 might fail to be absorbed by the soda lime. 
 
 After considerable experience in testing the methods by control 
 experiments of various kinds an arrangement of absorption tubes for 
 water and carbon dioxid was settled upon, and has skice proved very 
 satisfactory. The order is : First, a tube filled with pumice stone satu- 
 rated with sulphuric acid for the removal of water ; then two tubes 
 filled with soda lime for the absorption of the carbon dioxid ; and 
 finally a sulphuric-acid tube to absorb the water removed from the 
 soda-lime by tlie current of air and set free in the formation of carbon- 
 ates by the action of the carbon dioxid upon the hydroxids. 
 
 It was found important, however, to i)ass a current of dry air through 
 the suli)h uric-acid tubes for three or four hours before they were used 
 
29 
 
 iur the (letoiiiiiiiations. since it \v;i8 ol)seivecl tliiit the freslily lilled 
 tubes lost \veii;ht when dry air was lirst drawn throujih them, the h)ss 
 sonietiuies anioiuitiiiy to 20 liiilligraiiis. A i)lausibk^, exphmatioii of 
 this loss would be found in the assumption tliat iuconipletely oxidized 
 eompounds of sulpliur or introgeu whieh were either orijiinally present 
 ill the acid or were formed by its action on the orj^anic matter in the 
 pumice stone were removed by the air when lirst passed through the 
 tube. As the method for avoiding the error i)roved simple and effective, 
 we have not taken the time to in<juire more fully into the cause. 
 
 The determination of carbon dioxid by the above method is (piite 
 satisfactory, as was shown by numerous control exi)eriments. In one 
 experiment, for instance, which was fairly representative of all, 1.(>0JI2 
 grams of carbon dioxid were delivered into the air current and 1.071S 
 grams were removed in the soda-lime. 
 
 The weighings were all made with a counterpoise. To insure e(pnil 
 moisture condensation on the tubes and counteri)oise, the latter was 
 kcjit in the tiay with the U-tubcs, and hence subjected to like conditions 
 of temperature and moisture. 
 
 The accurate determination of water has been found less easy. The 
 difficulty ai)pears to rest not so much in the determination of moisture 
 in the current of air as in the getting of all the moisture into the cur- 
 rent. It is believed that one chief trouble here n)ay be the adhering of 
 moisture to the surfaces of the walls and other interior parts of the 
 apparatus and its absorption by the clothing of the subject and the 
 furniture in the respiration chamber. It is evident that for reliable 
 results two things are requisite. One is an accurate and convenient 
 method for the determination of water in a current of air, the other a 
 means for either making sure that all the water to be determined is 
 contained in the air current or that the amount not in that current 
 shall be determined in some other way. The water to be determined 
 is the whole given off from tlie body of the subject in the respiration 
 chamber, less tlie amount renioved in feces and urine. I'ractically this 
 means the water exhaled through the lungs and skin. I^'or our i)resent 
 l)uri»ose it uiay be designated as water of exhalation and taken as 
 including the watci- of respiration from the lungs and that of persi)ira- 
 tioM from the skin. Since the various dilhculties encountered in the 
 a<*curat«; determination of water had not been satisfactorily over(;ome 
 when these experiments were made, the results of such determinations 
 are not reported in this article. 
 
 Tlie test of the reliability of th(; methods for the determination of 
 the products given off from the body of the person in the respiration 
 chamber must be found in check experiments in which known (pianti- 
 ties of the same i)roducts will be given off' in the cinunber and deter- 
 mined in the air current by the methods used for the actual experiments. 
 
30 
 
 Numerous cbeck experiments of this kind preceded the experiments 
 with men reported beyond. Tlie results indicated that the determina- 
 tions of carbon dioxid ^yere reasonably accurate. The same was also 
 true of the water as iar as concerned the amounts actually contained 
 in the incoming and outgoing currents of air. It was not certain, how- 
 ever, that the moisture which was condensed upon the interior surface 
 of the apparatus (especially upon that part of the apparatus within 
 the chamber through which the cold water passed to carry away the 
 heat and to which the term heat absorbers has been applied) was the 
 same at the beginning as at the end of the experiment. The assump- 
 tion that the methods for the determination of carbon dioxid and water 
 in the currents of air and for the determinations of the amounts of 
 carbonic acid in the ai)paratus were reasonably accurate was further 
 substantiated by check experiments which followed the present experi- 
 ments with men. 
 
 The most satisfactory of these were made by burning ethyl alcohol 
 inside the chamber. Tlie determinations of carbonic acid differed by 
 less than one-half of 1 per cent from the theoretical. In other words, 
 for every 100 grams of carbon in the alcohol the measurements gave 
 from 99.1) to 100.4 grams. So far as concerns the determination of car- 
 bonic acid given off inside the apparatus, the only difference between 
 these check experiments with alcohol and the exj)eriments with men 
 reported beyond was in the measurement of the air current, which 
 could hardly have made any very important difference in the results. 
 It is believed, therefore, that the determination of carbon dioxid given 
 off by the men in tlie experiments beyond can not be very far from 
 correct.^ 
 
 ^Before the check experiments were made, arrangemonts were perfected by wlaieh 
 tlie abs()r2)tion apparatus could be weighed by the mau iuside the chamber, so that 
 the chauges in the amounts of water coudeused upon the surface of the absorbers 
 coukl be learned. The measurements of the volume of the air were made by the 
 improved apparatus referred to above. (Sec p. 20.) 
 
 •Jn the check experiments with alcohol the determinations of water could not be 
 made with the same accuracy as in the experiments with men, since in the latter case 
 the absorption appaiatus could be weighed by the person inside the chamber. It is, 
 however, possible so to regulate the combustion of the alcohol, and hence the pro- 
 duction of carbon dioxid, water, and heat, that the, amounts produced during a given 
 period at the beginning of an experiment shall ])e A^ery nearly the same as during a 
 like period at the end. Under these circumstances the amounts of water condensed 
 on the absorbers at the ends of the two periods will be approximately the same. 
 The control of the amount of water condensed upon the absorbers is facilitated by 
 the ease Avith whicii both the temperature of the interior of the apparatus and the 
 proi)ortion of water in the incoming air current may bo regulated. 
 
 In the check experiments made by burning alcohol m the chamber, pains were 
 takentoiuake the conditions of (1) temperature of interior of apparatus, (2) amount 
 of moisture biought into the apparatus by the incoming current of air, and (3) the 
 rate of combustion of alcohol approximately alike at the beginning and at the end 
 of each experiment. These periods were six hours or more each. The experiments 
 proper began at the end of the first period and ended at the close of the second 
 
31 
 
 VOLATII.K OIJliAN'lC COMroiNDS. 
 
 It has been foimd nece.ssaiy in experiments witli some animals, e. g., 
 oxen, to determine the qnautities of carbon in the hydrocarbons and 
 other vohitile orj^anic couiponnds given oflt" from tlie body. Of these 
 the most important appears to be marsli gas prodnced by tlie ferment- 
 ative action of bacteria in the large intestine. Witli men the qnantity 
 of such compounds produced is apparently very small. They were not 
 determined in the experiments here reported, although it will doubtless 
 be necessary to look for such compounds and jterhaps to determine 
 quantitatively their content of carbon and hydrogen in oxi)eriments 
 where the greatest accuracy is sought. 
 
 THE EXPERIMENTS. 
 
 The factors involved in a complete metabolism experiment and in 
 what is commonly called a respiration experiment are fully explained 
 on page 7. For reasons already given, the account of the respiration 
 experiments here reported include only the resnlts of measurements of 
 the income and outgo of nitrogen and carbon. The factors actually 
 determined and reported are: 
 
 Income. — Food, drink, and their content of nitrojicn, carbon, protein (N X n.25), fatH 
 
 (etlicr extract), carbohydrates (by dill'crence), mineral matter (ash). 
 Outi/ii. — Respiratory prodncts— carbon dioxid and its content of carbon. 
 
 Feces — nitrogen, carbon, protein (N X 6.25), fats (ether extract), carbohy- 
 drates (by difl'erencc), mineral matters (ash). 
 Urine — nitrogen, carbon. 
 
 As above explained, the experiments here reported involved digestion 
 experiments. The results of the latter are included in the descriptions 
 which follow. The determination of the digestibility of the several nutri- 
 ents of the food was made in the usual way, by comparing the amounts 
 of protein fat, carbohydrates, and mineral matter in the food and feces.' 
 The results of the digestion exi)eriments, however, misrepresent the 
 actual digestion of the food by i)ractically the amount of the metabolic 
 jiroducts in the feces. The error, however, is not large, and, so far as the 
 resi)iration exi)eriments are coiu^erned, it nuiy be left out of account 
 entirely, siiu.-e (he <piestion is the balance of total a(;tual income and 
 outgo of cheniiital elements and the metabolic products of the feces 
 are as truly a part of the outgo as the undigested residue of the food. 
 
 ]teriod, and covered generally from twenty-fonr to forty-eight hours. The determi- 
 nations of water in the tl)rco chock experiments ranged from 100.1 to 100.3 ptir cent 
 of the thioretlcal amount. Improvements were also made in the arrangements for 
 the determination of the (juantitics of hc;it given oil' l)y tlie body. 
 
 'See discnssion of this snliject in U. .S. iJept. Agr., Olhce of lOxiJerimcnt Stations 
 I'.nl. 21, pp. 56-73. 
 
32 
 
 THE DIET. 
 
 In these experiments tlie effort was made to have the conditions as 
 nearly normal as possible. To this end it was essential that: (1) The 
 diet be such as to agree with tlie subject, and (2) the quantities of 
 nntrieuts be such as to meet the actual needs of the body under the 
 conditions in which the subject was placed during the experiment. 
 
 To facilitate the right choice of the diet, observations on the ordinary 
 diet of the subject and a preliminary test of a number of days were 
 considered essential. Accordingly the subject was allowed to select 
 his own diet from a bill of fare limited only by the skill and appliances 
 for cooking available. In this way the selection of food was made such 
 as to suit the palate and not become so monotonous as to cause nausea 
 or any other derangement of the processes of digestion. The subjects 
 were inclined to take more food than was necessary for the rather 
 inactive life in the respiration chamber. It was important to provide 
 that the regimen during the experiment should be not only such as 
 would meet the actual needs as regards kinds and amounts of nutri- 
 ents, but should also be the same from day to day. 
 
 The latter i^oint is especially necessary. The actual income for a 
 given day or a given number of days is the amount digested and 
 absorbed during that period. If the food varies from day to day there 
 is no convenient means of learning to what extent the proportions of 
 nutrients digested vary with the food. Or, to put it in another way, 
 with varying diet the coefficients of digestibility of the several nutri- 
 ents, protein, fats, and carbohydrates, may change and it will be 
 impossible to tell how much is digested from each day's ration unless a 
 separate digestion experiment is made each day, which latter would 
 either reduce the period of each experiment to one day or involve very 
 considerable difficulties in the separation of the feces for each day. 
 Furthermore, only part of the food taken on a given day is absorbed 
 and used in the body on that day, and it is impossible to tell just when 
 the period during which it is being used begins and ends. If, therefore, 
 the diet varies from day to day, there is no way to learn how the vari- 
 ation affects the amounts actually absorbed from the alimentary canal 
 and used by the body on the different days during and immediately 
 following the days when the changes are made. 
 
 These considerations bring out one of the chief sources of uncertainty 
 in such experiments, namely, the impossibility of measuring exactly 
 the amount of material actually taken from the digestive tract and 
 brought into use by the body during a specitied period. It seemed 
 that the error would be materially reduced, if not eliminated, by pro- 
 viding the subject with a uniform diet for a long period and letting the 
 actual experiment be for a shorter period included within this longer 
 period. This gives an opportunity to utilize the longer period for a 
 digestion experiment, the results of whicli may be taken as a measure 
 of the quantities of nutrients taken up and used during the metabo- 
 lism experiment. 
 
In accordance witli these considerations, the subject commenced a 
 specitied regimen some days in advance of each experiment. To adjust 
 the quantities of food materials, so as to secure the proper proportions 
 of nutrients, estimates were made in advance by use of the figures for 
 composition of American materials/ The exact amounts of protein, 
 fats, and carbohj'drates were, of course, not learned until the analyses 
 were made. Fortunately, the actual composition as thus found was 
 very close to the atlvance estimates in every case. 
 
 "Meals were eaten three times daily at regular hours, thus conforming 
 as far as possible to ordinary custom. Drinking water was allowed at 
 all times, the weight used and the temperature, however, being care- 
 fully noted. The freedom allowed in the selection of diet added, it is 
 believed, materially to the success of the experiment, although the 
 number of different materials ma<le the analyses quite laborious. 
 
 Although the diet in each experiment was comparatively simple, a 
 considerable number of food materials were analyzed. The composi- 
 tion of the various foods is given in the following table: 
 
 Tabi.k 1. — Compoxition of food materials used in the experiments. 
 
 2690 
 
 2tin9 
 
 2704 
 2715 
 2t;!l5 
 2fi'.l8 
 2705 
 42:!8 
 42:!9 
 4248 
 4249 
 4228 
 42:i7 
 4227 
 424U 
 4247 
 4250 
 2697 
 2701 
 269:j 
 27o:{ 
 
 2724 
 2727 
 2726 
 272:i 
 2728 
 2694 
 2700 
 2708 
 2725 
 27119 
 2707 
 
 27 ri 
 
 BP«?f.fripd 1 
 
 do 2 
 
 do 3 
 
 do 4 
 
 KgfTs, boiled 1 
 
 .....do 2 
 
 do 3 
 
 Butttr 1 
 
 do 2 
 
 do 3 
 
 do 4 
 
 Clu-esoa 1 
 
 doa 2 
 
 Milk 1 
 
 do 2 
 
 do 3 
 
 do 4 
 
 CrackerM, milk 1 
 
 do 2 
 
 JJrend.rye > 1 
 
 do 2 
 
 IJrcad, white 3 
 
 do I 4 
 
 lircad.lirown j 4 
 
 4 
 4 
 1 
 2 
 3 
 4 
 (fc) 
 
 Oatinial 
 
 lii^aiiH, dri< d. ... 
 
 I'otatoi H, iMiilud 
 
 do 
 
 do 
 
 do 
 
 Ai()deH 
 
 IVaclies I 3 
 
 •Sugar (c) 
 
 Per ct. 
 
 4.64 
 
 4.85 
 
 4.73 
 
 5.48 
 
 2.07 
 
 1.99 
 
 2.41 
 
 .14 
 
 .16 
 
 .14 
 
 .18 
 
 4.29 
 
 4.07 
 
 .58 
 
 .54 
 
 .53 
 
 .53 
 
 1.78 
 
 1.6/ 
 
 1.47 
 
 1.43 
 
 1.31 
 
 1.48 
 
 .93 
 
 2.75 
 
 1.10 
 
 .35 
 
 .30 
 
 .37 
 
 .40 
 
 .04 
 
 .09 
 
 Per ct. 
 
 21.24 
 
 23.00 
 
 20.26 
 
 23.18 
 
 14.45 
 
 14.95 
 
 15.43 
 
 64.64 
 
 66.40 
 
 67.07 
 
 66.85 
 
 33. 43 
 
 35.80 
 
 7.27 
 
 6.79 
 
 0.17 
 
 0.01 
 
 44.00 
 
 44.01 
 
 25. 85 
 
 25. 63 
 
 25. 83 
 
 27. 82 
 
 22.27 
 
 41.15 
 
 11.37 
 
 8.00 
 
 9.54 
 
 9.08 
 
 9.77 
 
 5. r>9 
 
 4.87 
 
 42.06 
 
 Per ct. 
 3.35 
 3.43 
 ?.91 
 3.46 
 2.25 
 2.42 
 2.55 
 9.69 
 9.69 
 9.78 
 9.89 
 4.88 
 5.20 
 .94 
 1.00 
 1.02 
 1.00 
 6.54 
 7.08 
 2.37 
 3.97 
 3.77 
 3.89 
 3.13 
 5.83 
 1.57 
 1.27 
 1.36 
 1.48 
 1.41 
 .78 
 .57 
 6.45 
 
 Per ct. 
 
 58.9 
 
 56.4 
 
 60.3 
 
 53.5 
 
 73.3 
 
 72.4 
 
 69.2 
 
 9.2 
 
 8.9 
 
 8.1 
 
 8.9 
 
 44.1 
 
 39.7 
 
 85.9 
 
 85.9 
 
 85.9 
 
 86.2 
 
 5.7 
 
 5.5 
 
 39.0 
 
 40.4 
 
 39.1 
 
 35.6 
 
 47.2 
 
 8.9 
 
 72.8 
 
 80.8 
 
 76.8 
 
 74.8 
 
 75.8 
 
 86.7 
 
 89.3 
 
 oX 
 
 Per ct. 
 
 29.0 
 
 30.3 
 
 29.5 
 
 34.2 
 
 12.9 
 
 12.4 
 
 15.1 
 
 .9 
 
 1.0 
 
 .9 
 
 1.1 
 
 26.8 
 
 25.4 
 
 3.6 
 
 3.4 
 
 3.3 
 
 3.3 
 
 11.1 
 
 10.4 
 
 9.2 
 
 9.0 
 
 8.2 
 
 9.2 
 
 5.8 
 
 17.2 
 
 6.9 
 
 2.2 
 
 2.3 
 
 2.3 
 
 2.5 
 
 .2 
 
 .6 
 
 Per ct. 
 
 9.8 
 
 11.1 
 
 8.1 
 
 10.4 
 
 11.3 
 
 13.0 
 
 13.2 
 
 80.3 
 
 85.4 
 
 88.4 
 
 86.9 
 
 24. 5 
 
 27.0 
 
 4.2 
 
 4.5 
 
 4.5 
 
 4.2 
 
 12.3 
 
 12.2 
 
 .2 
 
 .2 
 
 1.3 
 
 1.4 
 
 1.2 
 
 7.0 
 
 .4 
 
 .1 
 
 . 1 
 
 .1 
 
 .1 
 
 .2 
 
 .1 
 
 o ^ 
 
 Per ct. 
 
 1.0 
 
 .7 
 
 1.2 
 
 4.0 
 
 5.5 
 
 5.5 
 
 5.5 
 
 5.6 
 
 09.6 
 
 69. 3 
 
 50.3 
 
 49.0 
 
 50.0 
 
 52.8 
 
 43.6 
 
 65.2 
 
 18.0 
 
 16.2 
 
 19.8 
 
 21.7 
 
 20.6 
 
 12.7 
 
 9.7 
 
 100.0 
 
 Per ct. 
 1.3 
 1.5 
 2.0 
 2.0 
 1.0 
 1.0 
 
 1.1 
 
 3.6 
 
 4.7 
 
 2.7 
 
 3.1 
 
 3.4 
 
 3.9 
 
 .8 
 
 .7 
 
 .8 
 
 .7 
 
 1.3 
 
 2.6 
 
 1.3 
 
 1.4 
 
 .8 
 
 1.0 
 
 2.2 
 
 1.7 
 
 1.9 
 
 .7 
 
 I.O 
 
 1.1 
 
 1.0 
 
 .2 
 
 .3 
 
 ■la 
 
 p^' 
 
 Calories. 
 2.494 
 2.758 
 2.424 
 2.904 
 
 1. 897 
 2.043 
 2. 123 
 8. 122 
 8.184 
 8. 4:t5 
 8. 169 
 3.800 
 4. 219 
 
 .836 
 
 .822 
 
 .807 
 
 .798 
 
 4.677 
 
 4.679 
 
 2.681 
 
 2. 007 
 
 2.735 
 
 2. 892 
 2. 305 
 4.409 
 1. 179 
 
 .787 
 .905 
 
 1.032 
 . 989 
 .547 
 .470 
 
 3.987 
 
 aTliem; two Hanipl<;M of cIii'<>hi- Ix-caiiio p.irtialiy de(;oin|)osfd beforo tlio doltMininatioii.s of carbon, 
 hydroKori, and lii^atH of combMHtioii coiibl bf! iiiad'o. Tlic figures for faclnrH iiiiiiicrl liavi- \mfu caliMi- 
 laU-d from \\n: jMT<-i-nlaj;<'H of pro! ••in, fatH. and carlioliydrati-H by im(!of I be indors 0.5:i, 0.765, and 0.41, 
 r^MiHclivcly, lor tlM-conlcrit of carbon, and 0.07, 0.12. and 00, rcs|>c<;tivi'ly, for Ibo liydro^'on contc^nt; 
 till- b<at» of conibiiHtion witc calciilutcd from tiio valucH previoiiHly found in two Biniilar aan)i)loH. 
 
 '/KxpcrinifiilH Noh. 3 and 4. 
 
 cKx peri Mien U Noh. 1, 2, 3, and 4. 
 
 ' 11. .S. Dcjtt. A^r., Odiiu- (iC Expcritnoiit Statiou.4 liul. 28. 
 2771— No. 44 3 
 
34 
 
 DAILY ROUTINE. 
 
 The digestion experiment which was made with each respiration 
 experiment commenced two or three days before the latter, but both 
 ended at the same time. On the second or third day of the digestion 
 experiment the subject entered the respiration chamber, but, in order 
 to insure normal conditions, the respiration experiment did not begin 
 until six hours after he had entered. This allowed the subject an 
 opportunity for arranging his furniture, the hygrometer, thermometer, 
 and other apparatus in the room, and permitted the establishment of 
 the needed equilibrium of temperature and moisture content in the 
 chamber preparatory to the respiration experiment itself. 
 
 The food and drink were passed in and the solid and liquid excreta 
 were removed through the food aperture in the side of the apparatus. 
 A comfortable temperature was maintained within the room by means 
 of a current of cold water, which passed through the pipes of the heat 
 absorbers inside the chamber and thus brought away the heat radiated 
 from the man's body. The temperature which best suited the feelings 
 of the subject, generally not far from 20° C, was maintained through- 
 out the whole of each experiment, except during one period of the last 
 exi)eriment, when the subject was engaged in hard muscular work. In 
 this case a very large amount of heat was given off' from the body, and 
 the current of cold water passing through the absorbers did not suffice 
 to prevent the temperature from rising at times to 23° or 24°. As this 
 high temperature was maintained for only a few hours at a time, it is 
 clearly an exception to the rule. 
 
 The occupants of the chamber passed the time in such ways as were 
 in general most agreeable under the circumstances. They observed 
 regular hours of eating and sleeping. There was, of course, almost no 
 opportunity for exercise. In the last experiment, however, a si^ecial 
 arrangement was made for vigorous muscular labor in lifting and 
 lowering a weight suspended from a pulley. This arrangement will 
 be described in connection with the other details of the exi:)eriment. 
 Abundant oj)portunity was given for reading, considerable conversa- 
 tion was held between the occupant and the men who did the work out- 
 side, and the monotony was also relieved from time to time by visitors. 
 
 Since the experiments went on day and night, relays of the force for 
 day and night work were, of course, necessary. During the day a 
 force of five or six persons was generally employed. During the night, 
 when the occupant of the chamber was asleep, the force was reduced 
 to three. 
 
 A brief description of the routine of one day will perhaps help to a 
 better understanding of the way in which the experiment was carried 
 out. The night force of operators was relieved at 7 o'clock a. m. At 
 that time the subject was awake and ready for breakfast. The assist- 
 ant, who had charge of the preparation and cooking of the food, pre- 
 pared the breakfast 5 the chemist of the night force changed the system 
 
I 
 
 35 
 
 of U tubes for analysis of the air. The day chemist proceeded to start 
 the i)assage of the air through the fresh system of tubes, and then 
 weighed the system which had just beeu removed; the readings of the 
 meter by which the ventilating current of air was measured, and of 
 temperature, barometric j^ressure, etc., were made. The subject, hav- 
 ing emptied the bladder at G a. m., passed out the liquid, and at the 
 same time the solid excreta. The readings of the hygrometer and 
 thermometer inside the apparatus were taken by the subject on rising, 
 and the observations were repeated once in two hours throughout 
 the day. Naturally, the inquiry regarding the subject's physical con- 
 dition, and any changes needed, received early attention in the morning. 
 
 Breakfast was ordinarily served at about half past 7 o'clock, dinner at 
 about half past 12 o'clock, and .supper at 6 o'clock. Drinking water 
 was given Mhenever desired, its weight and temjierature being noted. 
 
 The freezing apparatus required repacking with ice and salt about 
 once in two hours during the day and night; the rate of flow of water 
 through the aspirators by which the samples of air for analysis were 
 drawn was regulated every half hour. The temperature of the air of 
 the meter was recorded hourly. The freezers through which the outgoing 
 air passed were changed once in twelve hours, and the water condensed 
 in them was weighed. The absorption tubes for the water and carbon 
 dioxid of the air sami)les were changed once in six hours, at which time 
 the temperature of the aspirators, the temperature of the meter, and 
 the readings of the meter and of the air-pump register were recorded. 
 
 Concurrently with all of these operations, the analytical work was 
 carried on and completed as rai)idly as possible. 
 
 COMPUTATION OF RESULTS. 
 XITROGEN BALANCE. 
 
 Kitrof/cn in urine. — In the estimate of nitrogen balance the measure 
 of the nitrogen metabolized in the body during a given period is sought 
 in the nitrogen of the urine for a period of equal length. The i)eriod 
 is commonly a day of twenty-four hours. The jieriod for collecting the 
 urine, however, can not be coincident with that for whi(;h the nitrogen 
 metaljolism is to be measured, since some time isrecjuired for the metab- 
 olize<l nitrogen to be conveyed to the kidneys, passed into the bladder, 
 and afterwards excreted in the urine. The twenty-four-hour period for 
 iollccting tlu; urine must therefore begin and end later tiian the cor 
 i«*sp()ii(iing nitrogen-nuitabolism period of twenty-four hours. This 
 interval, during which the excretion of nitrogen lags behind the metab- 
 olism, may for convenience be termed the "nitrogen lag." Unfortu- 
 nately there ai«; few data for judging accurately as to the length of this 
 interval of lag. Indeed one of the most dillicult problems in experi- 
 ments of this class is to determine the actual source of the nitrogen 
 excreted in the urine — that is, to determine whether the identical nitro- 
 gen of the food is excreted in the urine after a short interval, or 
 
36 
 
 whefher the nitrogen becomes part of the body tissue and an equiva- 
 lent amount (derived from the body) is excreted. 
 
 Kolpakcha^ has recently made some interesting experiments with 
 dogs which bear on this problem. He compared the ratio of phospho- 
 rus and nitrogen and sulphur and nitrogen in the food and urine under 
 various dietary conditions, and also when no food was consumed. These 
 ratios were found to vary under the different dietary conditions. The 
 conclusion was reached that when the food supply was adequate very 
 little nitrogenous tissue was broken down, i. e., the nitrogen excreted 
 actually came from the food. An excess of protein eaten over the 
 amount required was stored up inside the cells of the protein tissue of 
 the body, but was not immediately made a part of the actual tissue. 
 It was simply reserve material. After a few days of fasting, this 
 reserve was exhausted and the body was then compelled to draw on its 
 own protein. Since the above-mentioned period is short, the conclusion 
 seems warranted that in the case of dogs the actual nitrogen consumed 
 in the food is soon excreted under ordinary conditions. 
 
 In the present experiments a lag of six hours was assumed in one case 
 and a lag of twelve hours in another. The fluctuations in the daily 
 excretion of nitrogen in the experiments herewith reported when the 
 diet and other conditions were reasonably uniform indicate, however, 
 that it is impossible to make any accurate estimate of this interval of 
 lag. These fluctuations are shown in the statistics of the nitrogen 
 excretion in Tables 5, 12, 19, and 26. 
 
 It is a familiar fact that some materials may be excreted by the urine 
 within a very short time after they have been taken in the food. Thus 
 it is a common observation that the peculiar odor of urine which comes 
 from asparagus may be observed within an hour after eating the latter. 
 In several rough tests made in this laboratory very small quantities 
 of i)otassium iodid were administered to a person, and a perceptible test 
 for iodin was obtained in the urine within half an hour after taking 
 the salt. 
 
 Such observations as these, however, do not give exact indications 
 of the rapidity of secretion and excretion of metabolized nitrogen. 
 Thus it was found, in experiment No. 4 (p. 51), where the metabolism 
 of nitrogen was materially increased by severe muscular work during 
 a period of three days, that the increase of nitrogen in the urine appar- 
 ently lagged a day behind the period of increased muscular exercise, 
 and after the muscular work stopped there was a similar lag in the 
 return of the nitrogen of the urine to the i)revious level of muscular 
 rest. In this case, however, the data do not exactly define the time of 
 rise aijd fall of nitrogen secretion or excretion. If the urine had been 
 collected and its nitrogen determined every six hours instead of mixing 
 the amount collected for twenty-four hours together and making but a 
 
 iPhysiologicheskii Sbornik., 1 (18S8),p.56. 
 
37 
 
 single analysis, as was actually done, the results might have given a 
 closer indication of the relation between the times of increased and 
 decreased metabolism and those of increased and decreased excretion 
 of nitrogeu. 
 
 The experiments here reported were divided into experimental days 
 of twenty-four hours. These experimental days were not calendar 
 days beginning at un<lnight, but were made to begin at such houis as 
 were most convenient. In experiment No. 4 the nitrogen .was col- 
 lected and examined during twenty-four hour ])eriods, each beginning 
 and ending six hours after the corresi)()nding ex])erimental day. The 
 arrangements and calculations for experiments 1 and ii were somewhat 
 dift'erent from those for experiments 3 and 4, as explained on page 49. 
 
 The principal factors involved in the computation of the nitrogen 
 balance may 1)6 stated as follows : 
 
 d) yUrogen of food. — This represents tlic gross income. 
 
 (2) Xitrogeii of feres. 
 
 i'.i) NUroi/dt of «?•(■««. — This is mainly the nitrogen of compounds from the food 
 and hody tissue which have not hccu completely oxidized, the most important hcing 
 urea. 
 
 Nos. '2 and 3 together make up the gross outgo of nitrogen. 
 
 (4) Nitrogen of food digiiiUd (Did ahsorhed and thus made available for use in thi' 
 body. This is the total nitrogen less th.it of the feces. Its amount is found hy sub- 
 tracting Xo. 2 from No. 1. It may be designated as " tot.'il available" nitrogen, i. e., 
 the total available for metabolism. 
 
 (5) Nitrogen gained or lout hij the hody. — If more nitrogen is taken into the body 
 than is given off — in other words, if No. ] is greater than the sum of Nos. 2 and .% or, 
 what is the same thing, if No. 4 is greater than No. 3 — the difference will 1)e the 
 amount the body has gained. If, on the other hand, the body has given off more 
 nitrogen than it has received, the difference. No. 3 less No. 4, is the, amount lost. It 
 is customary to multiply the amount gained or lost by 6.25 and to assume that the 
 product represents the gain or loss of i>rotein. 
 
 CAllBON IJALANCE. 
 
 In like manner the principal data involved in the computation of the 
 carbon balance may be succinctly groui)ed as follows: 
 
 (1) Carbon of food. — This is the gross income. 
 
 (2) Carbon of feces. 
 ( '.i ) Car bo n of urin e. 
 
 (i) Carbon of carbon dioxid exhaled. 
 
 NoH. 2, 3, and 4 together make u]i the gross outgo. 
 
 (.">) Carbon of fooil digested and absorbed and thus made avail.able for metabolism. 
 It is found by subtracting No. 2 from No. 1, and may be designated as " total avail- 
 able" «;arlion, i. e., t<»tal available for lufitaliolism. The (iarbon of the metabolic 
 jtroductH of the feces is here treated as if it were a i)art of the undigested residue 
 of the food. 
 
 (Ct) Carbon acluallg utilized. — This is the carbon absorbed less that excreted by 
 the kirlneys in the form of urea and other jtroducts of incomplete oxidation of 
 organic compoiiiidH. It is found by subtracting No. 3 from No. 5, and may be desig- 
 natid as "net available" carl)on, I. e., tiie total amount availabli' (or building tissue 
 or yielding euergy. 
 
38 
 
 (7) Carhon gained or lost iy the hody.—U No. 1 is greater than the snm of Nos. 2, 3, 
 and 4, or, what is the same thing, if No. 5 exceeds the sum of Nos. 3 and 4, the dif- 
 ference Avill represent the gain in carhon. If, on the other hand, the hody has lost 
 carhon the amount will he found hy suhtracting No. 5 from the sum of Nos. 3 and 4. 
 
 GAIN AND LOSS OF TROTEIN AND FAT. 
 
 The metliod usually followed in these computations is the one origi- 
 nally proposed by Pettenkofer and Voit and used by them and other 
 experimenters. It assumes that the nitrogen, carbon, and hydrogen 
 gained or lost by the body belongs to either protein compounds, fats, 
 or carbohydrates, and that these have definite proportions of nitrogen, 
 carbon, and hydrogen. On this basis the quantities of these three 
 elements gained or lost would serve as data for computation ot the gain 
 or loss of each one of the compounds. 
 
 Of course these assumptions are not entirely accurate, but they are 
 enough so for our present purpose. Even if they were accurate it 
 would be impossible to tell exactly how much of either class of com- 
 pounds was actually metabolized and actually stored in the body or 
 resolved into its constituents and given off' from the body. It would 
 only be possible to estimate the difference between the total amount 
 of each substance which was stored and the total amount which was 
 broken up and burned. As regards the protein stored or lost, it is 
 impossible to tell how much belongs to either cell tissue or cell contents, 
 or how much has simply formed a part of the blood or other fluids. 
 The case is entirely analogous with the fats and carbohydrates. But 
 it seems fair to assume that the increase or decrease of nitrogenous 
 material will be mainly that of the proteid compounds, which belong 
 IDroperly to connective and contractive tissue, and inasmuch as the 
 proportion of nitrogen in all these is approximately 10 per cent, the 
 quantity of protein gained or lost during the experiment corresponds 
 to very nearly 6.25 times that amount of nitrogen. With the nitrogen 
 of protein is a certain nearly constant amount of carbon. It is easy, 
 therefore, to compute the amount of the latter element Avhicli is either 
 stored by the body or lost from the body in protein. The algebraic 
 difference between the protein carbon gained or lost and the total car- 
 bon gained or lost represents the carbon gained or lost in carbohydrates 
 and fats. If we had the balance of hydrogen, or, better, the balance 
 of hydrogen and oxygen, and could assume definite quantities of car- 
 bon, hydrogen, and oxygen for the carbohydrates and fats, it would be 
 easy to calculate the amounts of these and of water actually gained or 
 lost. It is, however, common to assume that the quantity of carbohy- 
 drates in the body, which is very small, is not materially changed, and 
 that consequently the carbon gained or lost outside of that in the pro- 
 tein belongs to fat. Accordingly the gam or loss of carbon outside 
 that belonging to the protein gained or lost is taken as representing 
 the quantity of fat gained or lost. In calculations here used it is 
 assumed that the protein contains IG per cent of nitrogen and 53 per 
 cent of carbon, and that the fat contains 76.5 per cent of carbon. 
 
39 
 
 The method of conipatation may be expressed algebraically as follows : 
 Let the amount of gain or loss of nitrogen be represented by i K and 
 the amount of gain or loss of carbon by iO. Then: 
 ± N X 0.25 = protein gained or lost = i P 
 zt P X 0.53 = carbon gained or lost in protein = C (protein) 
 =t C ^ C (protein) =: carbon stored or lost as fat = C (fat) 
 ± C (fat) -^ 0.7(J5 = fat gained or lost. 
 
 The potential energy of the ingredients of food is commonly estimated 
 by the use of the factors proposed by llubiier,' which assign 4.1 calories 
 to each gram of protein or carbohydrates and 9.3 calories to each gram 
 of fat. This figure for protein, however, represents a net fuel value, 
 and is obtained by subtracting from the total fuel value of protein, 
 taken as o.~) calories per gram, the value for the nitrogenous comi^ounds, 
 including urea, not completely oxidized. 
 
 In the experiments here described the heats of combustion of the 
 food materials, feces, and dry matter of urine Averc determined directly 
 by the use of the bomb calorimeter, as above stated. The figures given 
 in the tables, therefore, represent the results of these determinations 
 rather than estimates made by the use of factors. In the computations 
 of energy of the protein and fat gained or lost from the body, however, 
 it is, of course, necessary to use factors. For protein gained or lost 
 tlie factor 5.5 was employed. For the fat gained or lost the factor 9.4 
 was used as representing tlie heat of combustion of liuman fat per gram. 
 
 The principal data involved in these comi)utations may be classified 
 as was done with those of nitrogen and carbon above. 
 
 (1) Total energy of nutrients of food, or total energy of income. 'I'liis is rei)resente(l 
 by the heats of comhustioii of the food materials. 
 
 (2) Enn-gy in feces, actual heats of comljiistion. 
 
 (3) Kiiergy in urine, boats of comlnistroii of dry matter. 
 
 (4) '/'olal energy in food digested and alimrhed. — This is usually found by subtracting 
 No. 2 from No. 1, and may be de8ignatc<l as total urailahle energy. This valu<' obtained 
 ]iy difference, liowevcr, does not exactly re])resent the fuel value realized from tlie 
 digeste<l food, for the reason that there is always a portion of digested food which 
 IS not com])letely oxidized — namely, the organic matter, mainly nitrogenous, which 
 is isecreti-d by the kidneys and excrcited in the urine. Assuming the organism to bo 
 in nitrogftu equilibrium, the heat of combustion of this partially oxidiztxl material 
 may be assumed to be that of tli(! water-free substance of the urine. For the diges- 
 tion experiment, in wliich the gain and loss of body material are left out of account, 
 it is most convenient to estiimite tins find value of this i)artly oxidized nilrogenous 
 material and 8ul>tract it from th<^ total heat of combustion of the digeste<l food. 
 For this ]iurpoHe it is assumed that the whole will be in the form of ure.a, and that 
 the amount of the latter will corresponil to the amount of digested nitrogen. 
 
 (.5) Set energy of food digmled and ahuorbed. — If jirotein is iieitluir gained nor lost, 
 the net energy is fouml liy subtracting No. 3 from No. 4. If protein is stored, No. !5 is 
 too small by the value of the urea and kindred comjiounds cornisponding to the 
 nitrogen in the prot<-in stored. If protein is lost, No. 3 is too large ))y the energy of 
 
 ' ZtHciir. Miol., 21 (IS85), p. 250. 
 
40 
 
 the urea which comes from the protein lost. The fuel value of urea correspondiug 
 to 1 gram of i^rotein is 0.87 calories.' 
 
 If, then, the protein stored or lost is multiplied by 0.87 and the product added to 
 No. 3 Avheu protein is stored and subtracted from it when lost, the energy of the 
 urine correspondiug to the protein digested is obtained. In other words, the net 
 energy of the food digested is No. 4 -(No. 3 J- 0.87 X protein gained or lost). 
 
 It is extremely probable that further consideration of the subject, together with 
 investigations now contemplated, may lead to more or less change in the details of 
 the method here employed for the estimation of energy of the compounds in ques- 
 tion, including especially the nitrogenous compounds. This method will, however, 
 suffice for the present use, which is only tentative. '^ 
 
 (6) Energy liberated as heat or manifested as external muscular work. — If a balance of 
 energy is to be made, another factor must be talten into account, namely, the heat 
 radiated from the body, and that equivalent to the external muscular work per- 
 formed. Though this was measured in the present experiment, for. the reason 
 already stated, the results are Avithheld, and the balance of income and outgo of 
 energy is not given. 
 
 RESPIRATION EXPERIMENT No. 1 (DIGESTION EXPERIMENT No. ]1). 
 
 The subject in this experiment was a Swede 29 years of age who 
 acted as Laboratory janitor and was accustomed to a moderate amount 
 of muscular work. He would be called a hearty eater. During the 
 X)rogress of the experiments he read a little for diversion, but the 
 larger part of the time was as free from mental and physical activities 
 as practicable. While he was entirely willing to do everything that 
 was required of him, it became evident that he did not find the sojourn 
 in the chamber entirely agreeable. Toward the end of the second 
 experiment he became somewhat ill, but the circumstances were such 
 that it could hardly be attributed to impure air or any other abnormal 
 condition ; indeed, there seemed to be good ground to believe that the 
 slight illness was caused by nervousness due to the sojourn in the res- 
 l^iration chamber and an undefined and unfounded fear that some 
 trouble might result. 
 
 The diet was comparatively simple. It was of his own selection 
 and was made up of such foods as he would have eaten under ordinary 
 conditions. Three meals a day were eaten. Water was consumed ad 
 
 lUrea, CON3H4, contains 46.67 per cent of nitrogen; consequently NX 2. 143= urea. 
 From the values obtained by Berthelot, Stohmanu, and others, the fuel value of urea 
 may be taken as 2.53 calories per gram. Assuming that all of the digested protein 
 is consumed in the body to urea, we can find the theoretical value of the urea cor- 
 responding to 1 gram of protein as follows: Weight of protein — 6.25 = weight of 
 nitrogen. Weight of N X 2.143:= weight of urea. Weight of urea x 2.53^heat of 
 combustion of urea. Or the heat of combustion of the urea corresponding to 1 gram 
 
 of protein is -^ — (C^K^ — =0.87 calorics. The subject of metabolism of energy is dis- 
 cussed in U. S. Dept. Agr., Office of Experiment Stations Bui. 21, p. 113. 
 
 2 Eubner, Ztschr. Biol., 21 (1885), p. 337. The results of the present experiments, 
 both those given beyond and others still unijublished, agree entirely with Kubner's 
 in showing that the heat of combustion of the dry matter in the urine is much 
 larger than that of the urea, which would correspond to the nitrogen in the urine. 
 
41 
 
 libitum. The foods coiisiiined at each meal are shown in the following 
 table : 
 
 Table 2. — Daily mvuit, respiration experiment Xo. 1 ((Uycstion experiment No. 11). 
 
 Breakfast. 
 
 Dinner. 
 
 Supper. 
 
 Egss, abont 
 
 Grams. 
 100 
 15 
 
 100 
 100 
 •JO 
 300 
 
 
 Grams. 
 121 
 20 
 300 
 150 
 150 
 
 
 Gram,*. 
 75 
 
 Butter 
 
 Butter 
 
 Milk 
 
 600 
 
 Milk 
 
 Milk 
 
 
 100 
 
 Bread 
 
 
 
 
 
 
 
 
 
 
 
 
 The digestion experiment was of longer duration than the respiration 
 expeiiiiiont. It began with breakfast February 15, 181)0, and ended 
 with dinnor February 10, covering four and two-thirds days and includ- 
 ing 14 meals. Of this period two and one fourth days (11 a. m. Feb- 
 ruary 17 until the close of the experiment) were i^assed in the respira- 
 tion chamber. Tlie weight of the subject (without clothing) at the 
 beginning of the latter period was Ofi.D kilograms (147^ i^ounds). The 
 total amount of each iood consumed and of the feces excreted during 
 tlie whole experimental period, the composition and fuel values of food 
 and fece."*, and the amount and percentage of each nutrient digested are 
 shown in Table 3. 
 
 T.\I!LK 3. 
 
 -Food eaten and digested during the whole experimental period, 43 days {diges- 
 tion experiment No. 11). 
 
 Labo- 
 ra- 
 tory 
 
 n am- 
 ber. 
 
 26'..6 
 2695 
 
 4238 
 422S 
 4227 
 2697 
 2693 
 2694 
 2722 
 
 Kind of food. 
 
 Beef, fried 
 
 E;rg8, boiled 
 
 Butttr 
 
 Cll(M-H.! 
 
 Milk 
 
 Crackers, milk . . 
 
 Bread, rye 
 
 Potatoes, boiled . 
 Sugar 
 
 2764 VcxfM 
 
 Total. 
 
 Amount digested. 
 Fuel value urea 
 
 Net amount digented . 
 Per cent digewted 
 
 Weight 
 
 for 
 experi- 
 ment. 
 
 Grams. 
 C04 
 497 
 175 
 300 
 4, 400 
 396 
 1,250 
 755 
 100 
 
 Total 
 organic 
 matter. 
 
 Grams. 
 240 
 127 
 153 
 158 
 582 
 368 
 746 
 140 
 100 
 
 2, 607 
 71 
 
 2,536 
 
 97.3 
 
 Protein 
 
 (NX6.25.) 
 
 Grams. 
 175 
 64 
 2 
 80 
 159 
 44 
 115 
 17 
 
 656 
 26 
 
 96.1 
 
 Fat. 
 
 Grams. 
 59 
 56 
 151 
 
 74 
 183 
 
 48 
 2 
 1 
 
 574 
 15 
 
 97.4 
 
 Carbo- 
 hvdrates. 
 
 4 
 
 240 
 270 
 629 
 122 
 100 
 
 1, 377 
 30 
 
 1,347 
 
 97.8 
 
 Fuel 
 value, 
 deter- 
 mined. 
 
 Calories. 
 
 1,506 
 
 943 
 
 1,421 
 
 1,266 
 
 3,078 
 
 1,852 
 
 3,351 
 
 594 
 
 399 
 
 15,010 
 500 
 
 14, 510 
 535 
 
 13, 975 
 93.1 
 
42 
 
 The amount, composition, and fuel value of the food during the two 
 and one-fourth days (Februaiy 17, 11 a. m., to February 19, 5 ]). m.) 
 passed in the respiration chamber are shown in the following table: 
 
 Table 4. — Food eaten during the period in the respiration chamler, 2^ days {respiration 
 
 experiment No. 1). 
 
 Labo- 
 ra- 
 tory 
 
 num- 
 ber. 
 
 Kind of food. 
 
 Weight 
 per day. 
 
 Nitro- 
 gen. 
 
 Carbon . 
 
 Protein 
 
 (NX 6.25.) 
 
 Fat. 
 
 Carbo- 
 
 by- 
 drates. 
 
 Fuel \ 
 
 Deter- 
 mined. 
 
 ralnes. 
 
 Calcu- 
 lated. 
 
 2696 
 
 One day, 3 meals. 
 Beef, fried 
 
 Grams. 
 
 121 
 
 98 
 
 35 
 
 75 
 
 1, 000 
 
 100 
 
 250 
 
 150 
 
 20 
 
 Grams. 
 5.61 
 2.03 
 .05 
 3.22 
 5.80 
 1.78 
 3.07 
 
 Grams. 
 25.70 
 14.16 
 22. 62 
 25. 07 
 72. 70 
 44.00 
 64.62 
 12.00 
 8.41 
 
 Grams. 
 35.1 
 12.7 
 .3 
 20.1 
 30.3 
 11.1 
 23.0 
 3.2 
 
 Grams. 
 11.8 
 11.1 
 30.2 
 18.4 
 41.5 
 12.3 
 .4 
 2 
 
 Gramas. 
 1.3 
 
 .9 
 54.5 
 09.6 
 125.8 
 24.3 
 20. 
 
 Calories. 
 302 
 186 
 284 
 285 
 836 
 408 
 670 
 118 
 80 
 
 Calories. 
 308 
 
 2695 
 
 
 181 
 
 4238 
 
 
 283 
 
 4228 
 
 
 285 
 
 4227 
 
 Milk .. 
 
 809 
 
 2697 
 2693 
 
 Crackers, milk 
 
 401 
 645 
 
 2694 
 2722 
 
 Potatoes, boiled 
 
 119 
 
 82 
 
 
 Total 
 
 
 
 
 
 
 22.68 
 
 289. 28 
 
 141.8 
 
 125.9 
 
 296.4 
 
 3,229 
 
 3,173 
 
 
 For dinner, Feb. 19. 
 
 
 
 2696 
 
 120 
 20 
 300 
 150 
 150 
 
 5.57 
 
 .03 
 
 1.74 
 
 2.20 
 
 .52 
 
 25.49 
 12.93 
 21.81 
 38.77 
 12.00 
 
 34.8 
 
 .2 
 
 10.9 
 
 13.8 
 
 3.2 
 
 11.7 
 
 17.3 
 
 12.4 
 
 .2 
 
 .2 
 
 1.3 
 
 "ie.'s' 
 
 75.4 
 24.3 
 
 299 
 162 
 251 
 402 
 118 
 
 306 
 
 4238 
 4227 
 2693 
 
 Butter 
 
 Milk 
 
 162 
 243 
 387 
 
 2694 
 
 Potatoes, boiled 
 
 Total 
 
 119 
 
 
 
 10.06 
 
 111. 00 
 
 62.8 
 
 41.8 
 
 117.3 
 
 1, 232 
 
 1, 217 
 
 
 Grand total, 2i 
 
 
 
 
 
 55.42 
 
 689. 56 
 
 319.2 
 
 293.6 
 
 710.1 
 
 7,690 
 
 7,563 
 
 
 
 
 
 On the days which the subject passed in the respiration chamber the 
 urine was collected also. In this and the following experiment it was 
 not collected after the subject left the apparatus,^ The urine was col- 
 lected from G p. m. on the day before the respiration experiment began 
 to 5 p. m. on the day the experiment ended. As the experiment began 
 at noon, the weights of urine excreted have been recalculated so as to give 
 the weights from noon to noon, instead of from p. m. to G p. m. In 
 doing this it was assumed that the amount secreted was uniform from 
 hour to hour, and that the amount for the original period, from 6 p. m. 
 to G p. m., could be divided into two parts proportional to the time, one 
 part being the amount from G p. m. to 12 m. the next day, the other 
 the amount from 12 m. to 6 p. m. The amount for the -short period of 
 six hours, from 12 m. to 6 p. m. of one day, was then added to the amount 
 for the longer period of eighteen hours, from G p. m. to 12 m. of the 
 following day, thus giving the total weight for the twenty-four hoars 
 from 12 m. to 12 m. Of course, this allows for no lag in the urine 
 (see page 35), but the error thus introduced is probably not very great. 
 The subject had been doing light manual labor before entering the 
 apparatus, and did no Avork during the exi)eriment. There may have 
 been a slightly larger amount of nitrogen in the urine of the first day 
 of the experiment than was actually metabolized during that day. 
 
 ^In experiments 3 and 4 it was collected for some time after, as stated in the 
 descriptions of those experiments. 
 
43 
 
 Such excess might have oeen due to the metabolizing of a larger 
 quantity of nitrogen during the day before the subject entered the 
 apparatus. Thus it is to be observed that the weight of uitrogeu 
 eliminated in all of the experiments, with the exception of the third, 
 is slightly smaller on the second day than on the lirst. 
 
 The amount of urine and feces excreted while the subject was in the 
 resi)irati<»n chamber and the nitrogen and carbon content and fuel 
 value of each are given in the following table: 
 
 Table 5.—Xitro(i)n and carhmi and fuel raliie of iirhir mid feces (respirafion experi- 
 ment jN'o. J). 
 
 I'riiie aud feces. 
 
 Frine (February 17-18, 12 m. to 
 12 in.) 
 
 Uriue (February 18-19, 12 m. to 
 12 m.) 
 
 Urine (February 19, 12 ni. to 5 
 p.ui.) 
 
 ToUl 
 
 Fece.s (average for 1 day) , 
 
 Total, 2 daj's 
 
 Auiount. 
 
 Grains. 
 1,395 
 
 1, ,313 
 260 
 
 2,968 
 21.9 
 43.8 
 
 Nitrogen. 
 
 Per et. Orams. 
 1.45 20.23 
 
 1.45 
 1.45 
 
 19.04 
 3.77 
 
 43.04 
 .95 
 1.82 
 
 Carbon. 
 
 Per ct. Orams. 
 0.84 I 11.72 
 
 11. 03 
 2.18 
 
 24. 93 
 8.98 
 17.90 
 
 Fuel 
 
 value per 
 
 gram. 
 
 Calories. 
 0.110 
 
 .110 
 .110 
 
 Total 
 
 fuel 
 
 value. 
 
 Calories. 
 154 
 
 145 
 
 28 
 
 327 
 107 
 214 
 
 The carbon dioxid produced by the subject was measured during the 
 period j>assed in the respiration chamber. For convenience in collect- 
 ing samples the day of twenty-four hours was divided into several 
 periods. The volume of air j)assiug through the respiration chamber, 
 the amount of carbon dioxid it contained per liter on entering and on 
 leaving the chamber, and the total amount excreted by the subject, as 
 well as the total amount of carbon in the excreted carbon dioxid are 
 shown in the following table: 
 
 Tablk 6. — Carbon dioxid produced in respiration experiment No. t. 
 
 Date. 
 
 February 17, 12in., to 
 FebniiirylS, 12iM. 
 
 February 18. 12 tn., to 
 February 19, 12 in. 
 
 February 19, 12 -n. \*t 
 5 p. in. 
 
 Period. 
 
 Ventila- 
 tion (vol- 
 ume of 
 air). 
 
 Liters. 
 fl2ui.to7p.m ' 21,724 
 
 '7 ji. III. to 2 a. Ill 
 
 |2 H. III. to 9 a. m ' 
 
 9 a. III. to 3 p. in.. .' 
 
 3 p. Ill tf) 10 p.m.. . 
 
 10 |i. m. to 4 a. m . . 
 
 4 a. 111. to 11 a. III.. 
 
 ill a. ni. to 5 p.m.. 
 
 21, 094 
 20, 566 
 
 20, 052 
 
 20, 300 
 19, 4.50 
 21,227 
 
 17, 933 
 
 CO-i per liter. 
 
 In incom- In outgo- 
 ing air. in g air. 
 
 Mg. 
 
 0.51 
 
 .61 
 .59 
 
 Mg. 
 
 12.48 
 
 10.28 
 8.01 
 
 13.39 
 9. 75 
 9.3(1 
 
 12.74 
 
 (jiven 
 otr by 
 subject. 
 
 Mg. 
 
 11.97 
 
 9.67 
 7.42 
 
 11.03 
 
 12.81 
 9.17 
 8.70 
 
 12. 15 
 
 Total 
 weight 
 CO^ ex- 
 haled by 
 subject. 
 
 Grains. 
 
 ( a 60. 4 
 
 I 260. 
 
 203. 9 
 
 152.7 
 
 / 116.6 
 
 I 6116.6 
 
 260. 4 
 
 178.4 
 
 184.7 
 
 / :t6.3| 
 
 I cisi.ej 
 
 Total 
 weight C 
 exhaled 
 in CO2. 
 
 Grains. 
 216.5 
 
 211.7 
 49.5 
 
 aTho air in the reHpiration chamber at the clo8^^ of the (^xiH^riiiient coiitaiiicfl more COj than at the 
 beginning. AiialVHeM ol Haiiiples, knowing the volume of air in Ilie <liaml)er, Hhowed Ibis diirerelicu 
 ill amount to bi- approximat<'ly 60.4 graiiiH. It is a.ssuiiK-d that tliis increa.se took place during the 
 Hint iweiityfour hours, on wliiVb assum|itlon 00.4 grams of ( 'O.^ <!X baled remained in t ho aji|)ariitus, 
 and hence was not deducted and measured by the regubir analyses. Accordingly thin amount of CO.^ 
 is athjixl to the amount found bv th4-. analysis for thi-. tlrst. twenty-four hours. 
 
 fcOf the jMrriod from a. m to 3 p. m.,' half belongs to the lirHl aud hull' to the second day of the 
 cx|M;rinii'nt. 
 
 eilf the periisl from 1 1 a. m to 5 p. m.. tUi- lirst hour belongs to the second day and the remainder to 
 the fracUou uf the third <biy of Ibo experiment . 
 
44 
 
 From the data of Tables 4, 5, and G the balance of income and outgo 
 of carbon and nitrogen is computed with results shown in Table 7. 
 
 In this and in the following experiment the subject passed two and 
 one-fourth days (fifty-four hours) in the respiration chamber, and the 
 nitrogen of the urine and the carbon of the carbon dioxid exhaled 
 were determined for this length of time. The number of meals taken, 
 however, was seven, which included two whole days and dinner on the 
 third day. It is, of course, impossible to say how much of the nutri- 
 ents and energy of the food eaten for dinner at 12 o'clock would be 
 utilized in the body before the close of the experiment at 5 o'clock. 
 There is a similar uncertainty as to how much of the outgo of feces 
 should be accredited to this quarter day. Accordingly, tlie results of 
 these two experiments have been calculated for the two whole days, 
 the fraction of a day at the close of the experiment being left out of 
 account. 
 
 Table 7. 
 
 -Balance of income and outgo of nitrogen and carhon (respiration experi' 
 mcnt No. 1). 
 
 
 Nitrogen. 
 
 Carbon. 
 
 Fuel value. 
 
 Date. 
 
 In 
 
 food. 
 
 In 
 urine. 
 
 In 
 feces. 
 
 Gain. 
 
 In 
 
 food. 
 
 In 
 urine. 
 
 In 
 feces. 
 
 In res- 
 pira- 
 tory 
 prod- 
 ucts. 
 
 Gain. 
 
 Of 
 food. 
 
 Of 
 urine. 
 
 Of 
 
 feces. 
 
 February 17-18, 12 m. 
 to 12ni 
 
 Gms. 
 22.7 
 
 22.7 
 
 Qms. 
 20.2 
 
 19.0 
 
 Qms. 
 0.9 
 
 .9 
 
 Qms. 
 1.6 
 
 2.8 
 
 Gms. 
 289.3 
 
 289.3 
 
 Gms. 
 11.7 
 
 11.0 
 
 Qms. 
 9.0 
 
 9.0 
 
 Gms. 
 216.5 
 
 211.7 
 
 Gm,s. 
 52.1 
 
 57.6 
 
 Calo- 
 ries. 
 3,229 
 
 3,229 
 
 Calo- 
 ries. 
 154 
 
 145 
 
 Calo- 
 ries. 
 107 
 
 February 18-19, 12 m. 
 
 107 
 
 
 
 Total, 2 days... 
 
 45.4 
 
 39.2 
 
 1.8 
 
 4.4 
 
 578.6 
 
 22.7 
 
 18.0 
 
 428.2 
 
 109.7 
 
 6,458 
 
 299 
 
 214 
 
 As explained on p. 38, the amount of protein gained or lost by the 
 body may be computed from the gain or loss of nitrogen, and the amount 
 of fat stored or lost by the body maybe computed from the gain or loss 
 of carbon, taking into account also the carbon in the protein gained or 
 lost. The resultS'of such computations are given in the following table: 
 
 Table 8. — Gain or loss of protein and fat in respiration experiment No. 1. 
 
 Date. 
 
 Nitrogen 
 gained.; 
 
 Protein 
 gained. 
 
 Total car- 
 bon 
 gained. 
 
 Carbon in 
 protein 
 gained. 
 
 Algebraic 
 difference be- 
 tween total 
 carbon and 
 carbon in pro- 
 tein (=M). 
 
 Fat 
 
 gained 
 
 (M-- 0.765). 
 
 February 17-18, 12 m. to 12 m 
 
 February 18-19, 12 m. to 12 m 
 
 Grams. 
 1.6 
 
 2.8 
 
 Grams. 
 10.0 
 17.5 
 
 Grams. 
 52.1 
 57.6 
 
 Grams. 
 5.3 
 9.3 
 
 Grams. 
 46.8 
 48.3 
 
 Orams. 
 6L2 
 63.1 
 
 Total, 2 days 
 
 4.4 
 
 27.5 
 
 109.7 
 
 14.6 
 
 95.1 
 
 124.3 
 
 
 
 The table indicates that during the two days of the experiment 27.5 
 grams of protein and 124.3 grams of fat were stored up in the body. 
 
45 
 
 RESPIRATION EXPERIMENT No. 2 (DKiESTION EXPERIMENT No. 12). 
 
 This experiment was made with the same subject and under the same 
 conditions as experiment No. 1. The digestion experiment began with 
 brealifast February 24, 1800, and ended with dinner February 28, mak- 
 ing 14 meals, or four and two-thirds days. The period from 11 a. m., 
 February 2G, to the close of the experiment, at 5 p. m., February 28, 
 covering two and one-fourth days, and inchiding 7 meals, was spent in 
 the respiration chamber. Tlie weight of the subject at the beginning 
 of the experiment (without clothing) was 07.5 kilograms (148^ pounds). 
 The daily menu was as follows : 
 
 Table 9. — Daily menu, respiration experiment Xo. 2 {digestion experiment Xo. 12). 
 
 Breakfast. 
 
 Eggs, aliont. 
 
 Butter 
 
 Milk 
 
 Bread 
 
 Sugar 
 
 Cofl'ee, about 
 
 Grains, 
 100 
 15 
 100 
 100 
 20 
 300 
 
 Dinner. 
 
 Cooked meat 
 
 Butter 
 
 Milk 
 
 Bread 
 
 Potatoes .... 
 
 Grams. 
 121 
 20 
 300 
 150 
 150 
 
 Supper. 
 
 Clicese 
 
 Milk 
 
 Milk crackers 
 
 Sugar 
 
 Co3ee, about . 
 
 Graing. 
 
 75 
 100 
 100 
 
 20 
 300 
 
 Tables 10 and 11 show the amounts, composition, and fuel values of 
 tlie food and feces and tlie coefficients of digestibility for the whole 
 l)eriod (four and two-thirds days) and the amount, composition, and 
 fuel value of the food during the period in the respiration chamber 
 (two and one-fourth days). 
 
 Tablk 10. — Food eaten and digested during the whole experimental period, 4^ days 
 {digestion experiment Xo. 12). 
 
 Labo- 
 ra- 
 tory 
 
 IIUUl- 
 
 ber. 
 
 Kind of food. 
 
 Weight 
 
 for 
 experi- 
 ment. 
 
 Total 
 organic 
 matter. 
 
 Protein 
 
 (NX 0.25) 
 
 Fat. 
 
 Carbo- 
 hydrates 
 
 Fuel 
 value, 
 deter- 
 mined. 
 
 2699 
 2»;98 
 4_'3'.t 
 4237 
 4240 
 2701 
 2703 
 27<>0 
 2722 
 
 Beef. friPtl 
 
 Ek-s, boiled 
 
 Hiitter 
 
 Cbeeso 
 
 Milk 
 
 Craekers, milk. . 
 
 Bread, rye 
 
 Potat^ies, boiled. 
 Sugar 
 
 2760 Feces 
 
 Total. 
 
 Anioiinldigestcd- 
 Fuel value urea 
 
 Net amount digested. 
 Per cent digcstetl 
 
 Grams. 
 515 
 49H 
 175 
 300 
 
 L', 400 
 400 
 
 1, 130 
 
 eoi 
 
 180 
 
 Grams. 
 217 
 127 
 151 
 1G9 
 321 
 3(iH 
 CCl 
 146 
 180 
 
 rains. 
 160 
 62 
 2 
 70 
 81 
 42 
 102 
 30 
 
 Grains. 
 
 57 
 
 65 
 
 149 
 
 81 
 
 108 
 
 49 
 
 2 
 
 1 
 
 Grams. 
 
 12 
 132 
 
 277 
 .557 
 115 
 180 
 
 Calories. 
 1, 4.30 
 1,017 
 i, 432 
 1,266 
 1, 973 
 1,872 
 2,961 
 638 
 718 
 
 2,340 
 81 
 
 555 
 46 
 
 512 
 15 
 
 1,273 
 20 
 
 13, 313 
 542 
 
 2, 2.59 
 
 1,253 
 
 12,771 
 448 
 
 91.7 
 
 97.1 
 
 12, 323 
 92.6 
 
46 
 
 Tai'.le 11. — Food eaten and digested during the period in the respiration chamher, 2J days 
 {resjnration experiment Xo. 2). 
 
 Labo- 
 ra- 
 tory 
 num- 
 ber. 
 
 2699 
 2698 
 4239 
 4237 
 4240 
 2701 
 2703 
 2700 
 2722 
 
 2699 
 4239 
 4240 
 2703 
 2700 
 
 Kind of food. 
 
 One day, 3 meals. 
 
 Beef, fried 
 
 Eggs, boiled 
 
 Butter 
 
 Clieese 
 
 Milk 
 
 Crackers, milk . . 
 
 Bread, rye 
 
 Potatoes, boiled . 
 Sugar 
 
 Total. 
 
 For dinner, Feb. : 
 
 Beef, fried 
 
 Butter 
 
 Milk 
 
 Bread, rye 
 
 Potatoes, boiled . 
 
 Total. 
 
 Grand total, 2i 
 
 Weight 
 per 
 day. 
 
 Oranns. 
 
 121 
 
 101 
 
 35 
 
 75 
 
 500 
 
 100 
 
 228 
 
 150 
 
 40 
 
 31 
 20 
 300 
 80 
 61 
 
 Nitro- 
 gen. 
 
 Grams. 
 5.87 
 2.01 
 
 .00 
 3.05 
 2.70 
 1.67 
 3.26 
 
 .54 
 
 1.50 
 
 .03 
 
 1.62 
 
 1.14 
 
 .22 
 
 4.51 
 
 Carbon. 
 
 Grains. 
 27.83 
 15.10 
 23.24 
 26.85 
 33.95 
 44.01 
 58.44 
 14.31 
 16.82 
 
 260. 55 
 
 7.13 
 13.28 
 20.37 
 20.50 
 
 5.82 
 
 67.10 
 
 Protein 
 
 (NX6.25). 
 
 Grains. 
 36.7 
 12 6 
 .3 
 19.1 
 16.9 
 10.4 
 20.4 
 3.4 
 
 9.4 
 
 .2 
 
 10.1 
 
 7.2 
 1.4 
 
 28.3 
 
 267.9 
 
 Fat. 
 
 Grams. 
 13.4 
 13.1 
 29.9 
 20.3 
 22.5 
 12.2 
 . 5 
 .1 
 
 Carbo- 
 hy- 
 drates. 
 
 Grams. 
 0.9 
 
 3.4 
 17.1 
 13.5 
 
 3.0 
 27.5 
 68.5 
 111.8 
 29.6 
 40.0 
 
 281.3 
 
 16.5 
 39.2 
 13.0 
 
 631.5 
 
 Fuel values. 
 
 Deter- 
 mined. 
 
 Calories. 
 337 
 206 
 286 
 317 
 411 
 468 
 594 
 145 
 160 
 
 2,924 
 
 86 
 164 
 247 
 
 208 
 59 
 
 6,612 
 
 Calcu- 
 lated. 
 
 Calories. 
 330 
 198 
 280 
 305 
 415 
 452 
 575 
 141 
 164 
 
 2,f 
 
 84 
 160 
 249 
 202 
 
 61 
 
 6,476 
 
 The amounts of urine and feces excreted during the period in the 
 respiration chamber and the nitrogen and carbon content and fuel 
 value of each are shown in the following table : 
 
 Table 12. 
 
 -Nitrogen and carbon and fuel value of urine and feces (respiration experi- 
 ment No. 2). 
 
 Labo- 
 ra- 
 tory 
 
 num- 
 ber. 
 
 Urine and feces. 
 
 Amount. 
 
 Nitrogen. 
 
 Carbon. 
 
 Fuel 
 
 value per 
 
 gram. 
 
 Total 
 
 fuel 
 
 value. 
 
 5018 
 
 Urine (February 26-27, 12 m. to 
 12 m.) 
 
 Grams. 
 969 
 
 913 
 
 190 
 
 Per ct. 
 1.92 
 
 1.92 
 
 1.92 
 
 Grams. 
 18.60 
 
 17.53 
 
 3.65 
 
 Per ct. 
 1.52 
 
 1.52 
 
 1..52 
 
 Grams. 
 14.73 
 
 13.88 
 
 2.89 
 
 Calories. 
 0.169 
 
 .169 
 
 .169 
 
 Calories. 
 164 
 
 
 Urine (February 27-28, 12 m. to 
 12 m.) 
 
 154 
 
 
 Urine (February 28, 12 m. to 5 
 
 32 
 
 
 Total 
 
 
 
 2,072 
 23.8 
 47.6 
 
 "'e.'es' 
 
 39.78 
 1.58 
 3.16 
 
 "41.49 
 
 
 3L50 
 
 9.87 
 19.74 
 
 
 350 
 
 276.5 
 
 Feces (average for 1 day) 
 
 Total, 2 days 
 
 4.886 
 
 116 
 
 232 
 
 
 
 
 
47 
 
 The carbon dioxid produced during the period in the respiration 
 chamber is shown in the followiug table : 
 
 Table 13. — Carbon dioxid produced in respiration experiment iVo. 2. 
 
 
 Period. 
 
 Ventila- 
 tion 
 (volume 
 ©fair). 
 
 CO2 per liter. 
 
 Total 
 
 Total 
 
 Date. 
 
 In incom- 
 ing air. 
 
 In outgo- 
 ing air. 
 
 Given 
 
 otf by 
 
 subject. 
 
 Me^dbv -^^d 
 subject. '° ^^•^• 
 
 Febmary 26. 12 m.,to 
 February 27, 12 m. 
 
 February 27, 12 m., to 
 February 28, 12m. 
 
 February 28, 12 m. tol 
 5 p. m. / 
 
 fl2m.to6p m 
 
 le p.m. to 1 .a.m... 
 
 1 a.m. to 7 a. m 
 
 7 a.m. to 2 p. m 
 
 2 p.m. to 9 p. m 
 
 9 p.m. to 4a. m 
 
 4 a. m to 10.30 a.m. 
 
 10.30a.m.to5p.m. 
 
 Litert. 
 21,064 
 
 20, 932 
 20, 686 
 
 21, 880 
 
 22, 492 
 22, 900 
 22, 216 
 
 21, 607 
 
 Mg. 
 
 0.56 
 
 .57 
 .59 
 
 .60 
 
 .54 
 .00 
 .61 
 
 .58 
 
 Mg. 
 
 11.63 
 
 11.50 
 8.06 
 
 11.20 
 
 12. Co 
 8.45 
 9.16 
 
 10.92 
 
 Mg. 
 
 11.07 
 
 10.93 
 7.47 
 
 10.60 
 
 12.11 
 7.85 
 8.55 
 
 10.34 
 
 Grams. \ 
 1 53. 2 
 233.2 
 228.8 
 154.5 
 / 165. 6 
 I ■•'66.3 
 272. 3 
 179.8 
 190.0 
 f 52.1^ 
 \ »171.3/ 
 
 Grains. 
 227. 8 
 
 207. 3 
 46.8 
 
 ' The air in the respiration chamber at the close of the experiment contained more CO2 than at the 
 l>eginning. Analyses of samples, comijured with the volume of air in the chamber, showed tliis 
 ditierenee in amount to be api)roxiniately 53.2 grams. It is as.sumed tliat this iucrejwe took ))laee 
 during the tirst twenty-four hours, on wliich assumption 53.2 grams of COj exhaled remained in the 
 apparatus, and hence was not deducted and measured by the' regular analyses. Accordingly, this 
 amount of CUj is added to the amount found by the analysis for the first twenty-four hours. 
 
 -Of the period from 7 a. m. to 2 p. m., five hours belong to the first, and the remainder to the second 
 day of the experiment. 
 
 5 Of the period from 10.30 a. m. to 5 p.m., the tirst one and one-half hours belong to tho second 
 day and the remainder to the fraction of the third day of the experiment. 
 
 Table 14 shows the balance of income and outgo of nitrogen and car- 
 bon. The figures are computed from data given in Tables 11, 12, and 13. 
 
 Table 1-4. — Balance of income and outqo of nitrogen and carion {respiration experiment 
 
 No. 2). 
 
 
 Kitrogen. 
 
 Carbon. 
 
 Fuel value. 
 
 Date. 
 
 In 
 food. 
 
 In 
 urine. 
 
 In 
 
 feces. 
 
 Gain 
 
 (+)">■ 
 loss 
 
 (-)• 
 
 In 
 food. 
 
 In 
 urine. 
 
 In 
 feces. 
 
 In res- 
 pira- 
 tory 
 prod- 
 ucts. 
 
 Gain 
 
 (+) or 
 
 loss 
 
 Of 
 food. 
 
 Of 
 urine. 
 
 Of 
 feces. 
 
 Febmary 26-27. 12 
 m. to 12 111 
 
 February 27-28, 12 
 m. to 1*2 in 
 
 Gms. 
 19.2 
 
 19.2 
 
 Gms. 
 18.6 
 
 17.5 
 
 Gms. 
 1.6 
 
 1.6 
 
 Gms. 
 —1.0 
 
 H0.1 
 
 Gms. 
 260.6 
 
 260.6 
 
 Gm^. 
 14.7 
 
 13.9 
 
 Gms. 
 9.9 
 
 9.9 
 
 Gms. 
 227. 8 
 
 207.3 
 
 Gms. 
 + 8.2 
 
 +29.5 
 
 Galn- 
 ries. 
 2, 924 
 
 2,924 
 
 C'alo- 
 
 rie.i. 
 
 164 
 
 154 
 
 Calo- 
 ries. 
 116 
 
 116 
 
 Total, 2 days. 
 
 38.4 
 
 36.1 j 3.2 1 —0.9 
 
 521.2 
 
 28.6 
 
 19.8 
 
 435.1 
 
 +37.7 
 
 5,848 
 
 318 
 
 232 
 
 The calculated gains or losses of protein and fat are show n in Table 15. 
 Tablk 15. — Gain or loss of i>roiein and fat {respiration experiment No. 2). 
 
 Date. 
 
 Nitrogen 
 gained ( + ) 
 orloBt(— ). 
 
 Protein 
 gained ( 1 ) 
 orlost(— ). 
 
 Grams. 
 -6.3 
 + 0.6 
 
 Tolal 
 carbon 
 gained. 
 
 Carbon in 
 
 protein 
 gained ( + ) 
 or lost (— ). 
 
 Algebraic 
 
 dili'erenee 
 between 
 
 t^ital car- 
 bon and 
 
 carbon in 
 protein 
 (-M). 
 
 Fat 
 gained 
 (M : 
 0.765). 
 
 February 26-27, 12 m. to 12 m . . . 
 February 27 28, 12 in. to 12 m . .. 
 
 Grams. 
 -1.0 
 +0.1 
 
 Grams. 
 1- 8.2 
 129.5 
 
 Grams. 
 —3.3 
 10.3 
 
 Grams. 
 
 1 11.5 
 +29. 2 
 
 Grams. 
 + 1.5.0 
 1 38. 2 
 
 Total, 2 dayfl .. .... 
 
 -0.9 
 
 —5.7 
 
 +37.7 
 
 -3.0 
 
 + 40.7 
 
 +53. 2 
 
 
48 
 
 RESPIEATIOK EXPERIMENT No. 3 (DIGESTION EXPERIMENT No. 13). 
 
 In this experiment the methods had been considerably improved and 
 the force of observers enlarged, advantage being taken of the experi- 
 ence gained in the two previous experiments. The subject was a 
 chemist (O. F.T.) 24 years old. The experiment began with breakfast 
 March 13 and ended with breakfast March 21, 1896, thus covering eight 
 and one- third days and including 25 meals. The respiration experiment 
 proper covered the 5 days with 15 meals from 11 a. m. March 6 to 11 
 a. m. March 21, inclusive. The weight of the subject at the beginning 
 of the experiment (without clothing) was 57.2 kilograms (126 pounds). 
 The subject was accustomed to rather less muscular labor than tlie 
 subject of the first two experiments. Pie was also rather lighter in 
 weight. During the experiment he performed as little muscular labor 
 as possible. He passed the time in resting, with light reading for 
 diversion. The diet, which he himself selected, was somewhat smaller 
 than that of the subject of the first two experiments and furnished 
 considerably less protein and energy. 
 
 The daily menu throughout the experiment was as follows: 
 
 Table 16. — Daily menu, respiration experiment No. 3 (digestion experiment No. 13). 
 
 Breakfast. 
 
 Eggs > 
 
 Butter 
 
 Milk 
 
 Bread 
 
 Sugar 
 
 Apples 
 
 Tea or coffee, about 
 
 Or 
 
 ams. 
 
 113 
 10 
 
 100 
 75 
 20 
 85 
 
 300 
 
 Dinner. 
 
 Cooked beef 
 
 Butter 
 
 Milk 
 
 Bread 
 
 Sugar 
 
 Potatoes 
 
 Peaches or pears . . . 
 Tea or coffee, about 
 
 Grams. 
 
 95 
 
 10 
 
 60 
 
 75 
 
 20 
 
 130 
 
 150 
 
 300 
 
 Supper. 
 
 Milk 
 
 Bread 
 
 Sugar 
 
 Peaches or pears 
 
 Qrams. 
 
 500 
 
 125 
 
 10 
 
 200 
 
 The amounts, comi)osition, and fuel values of the food and feces and 
 the coefficients of digestibility for the whole period (eight and one-third 
 days), and the amount, composition, and fuel value of the food for the 
 period in the respiration chamber (five days) are shown in the follow- 
 ing tables: 
 
 Table 17. — Food eaten and digested during the whole experimental period, d>\ days {diges- 
 tion experiment No. IS). 
 
 Labo- 
 ra- 
 tory 
 num- 
 ber. 
 
 2704 
 2705 
 4248 
 4247 
 2724 
 2708 
 2709 
 2707 
 2706 
 2722 
 
 Kind of food. 
 
 Beef, fried 
 
 Eggs, boiled 
 
 Butter 
 
 Milk 
 
 Bread 
 
 Potatoes, boiled . 
 
 Apples 
 
 Peaches 
 
 Pears 
 
 Sugar 
 
 Total. 
 
 Weight 
 
 for 
 experi- 
 ment. 
 
 Qrams. 
 
 766 
 
 904 
 
 170 
 
 5,380 
 
 2,275 
 
 2,300 
 
 755 
 
 1,400 
 
 1,400 
 
 400 
 
 .^^^± Protein 
 
 Se" (^><«-25) 
 
 Grams. 
 289 
 256 
 152 
 717 
 1,367 
 554 
 99 
 146 
 277 
 400 
 
 4,257 
 
 Gramt. 
 
 227 
 
 137 
 
 2 
 
 178 
 
 187 
 
 52 
 
 2 
 
 Grams. 
 
 62 
 
 119 
 
 150 
 
 245 
 
 30 
 
 3 
 
 1 
 
 2 
 
 1 
 
 Carbo- 
 hydrates. 
 
 Grams. 
 
 294 
 1,150 
 499 
 96 
 136 
 273 
 400 
 
 2,848 
 
 Fuel 
 value, 
 deter- 
 mined. 
 
 Calorics. 
 1,857 
 1,919 
 1,434 
 4,341 
 6,222 
 2,373 
 413 
 666 
 1,121 
 1,595 
 
 21, 941 
 
49 
 
 Tai-.le 17. — Food ealin and d'ujisltd dnrimj the whoh exjiirimviitdl period, etc. — Cont'd. 
 
 Labo- 
 ra- 
 tory 
 
 u um- 
 ber. 
 
 Weight 
 
 Kiud of foo.1. •'"^' . 
 experi- 
 
 iiieut. 
 
 Total 
 organic 
 matter. 
 
 Protein 
 
 (K A 6.25). 
 
 Fat. 
 
 Carbo- 
 hydrates. 
 
 Fuel 
 value, 
 deter- 
 mined. 
 
 2760 
 
 1 Grains. 
 Feces 131 
 
 Gravis. 
 97 
 
 Grains. 
 44 
 
 Grams. 
 
 20 
 
 Grams. 
 33 
 
 Calories. 
 628 
 
 
 
 4,160 
 
 752 1 59:i 
 
 
 
 Fuel value urt-a 
 
 
 654 
 
 
 Not aiiionut digested 
 
 
 
 
 
 
 
 
 20, 659 
 94.2 
 
 
 Per cent digested 
 
 97.7 
 
 94. 5 96. 7 
 
 98.9 
 
 T.VHLK 18. — Food eatiii di(riuij thr period in the rei^piration chamher, 'i days {respiration 
 
 experiment No. 3). 
 
 Labo- 
 ra- 
 tory 
 num- 
 ber. 
 
 2704 
 2705 
 4248 
 4247 
 2724 
 2708 
 2709 
 2707 
 2706 
 2722 
 
 Kind of food. 
 
 Five days, IS meals. 
 
 Beef, fried 
 
 EggH, boiled 
 
 Butter 
 
 Milk 
 
 Bread 
 
 Potatoes, boiled . 
 
 Apples 
 
 Peaches 
 
 Pears 
 
 Sugar 
 
 I Total 
 
 : Quantities per day 
 
 Weight 
 
 for I 
 
 5 days. 
 
 Nitro- 
 
 Grams. 
 
 481 
 
 502 
 
 100 
 
 3, 300 
 
 1,875 
 
 1,350 
 
 425 
 
 700 
 
 1,050 
 
 230 
 
 Grams. 
 
 22. 75 
 
 12.10 
 
 .14 
 
 17.49 
 
 18.01 
 
 4.99 
 
 .17 
 
 .63 
 
 .42 
 
 70. 71) 
 15.34 
 
 Carbon. 
 
 Grams. 
 97.43 
 77.40 
 67.07 
 203. 60 
 355. 10 
 130. 70 
 23.76 
 34.09 
 85. 57 
 96.74 
 
 Protein 
 (XX6.25). 
 
 Grams. 
 
 142. 2 
 
 75.6 
 
 .9 
 
 109.2 
 
 112.9 
 
 30.5 
 
 1.0 
 
 5.0 
 
 2.2 
 
 1,171.52 
 234. 30 
 
 479.5 
 95.9 
 
 Fat. 
 
 Grams. 
 
 38.7 
 
 66. 3 
 
 88.4 
 
 150.0 
 
 18.0 
 
 1.5 
 
 .7 
 
 1.3 
 
 1.0 
 
 365.9 
 73.2 
 
 Carbo- 
 
 li.V- 
 drates. 
 
 Grains. 
 
 180.5 
 695.4 
 293. 
 54.0 
 85.0 
 170.7 
 210.0 
 
 1, 688. 6 
 337.7 
 
 Fuel values. 
 
 Deter- 
 mined. 
 
 Calories. 
 
 1,166 
 
 1,066 
 
 843 
 
 2,663 
 
 3,760 
 
 1,393 
 
 232 
 
 333 
 
 841 
 
 917 
 
 13, 214 
 2,643 
 
 Calcu- 
 lated. 
 
 Calorics. 
 
 1, 145 
 
 1, 032 
 
 826 
 
 2,737 
 
 3,644 
 
 1,383 
 
 235 
 
 388 
 
 718 
 
 861 
 
 12,969 
 2,594 
 
 Table 19 shows the amounts of urine and feces excreted during the 
 period in tlio resi)iratiou chamber and the nitrogen and carbon content 
 and fuel value of each. In this table a 12-hour lag is allowed in calcu- 
 lating the urine and feces (see p. 35). In the light of the results 
 obtained in the succeeding experiment this seems to be more nearly- 
 accurate than tlie 0-hour lag. The time allowed for lag is, however, 
 probably of comparatively little importance, as the diet and occupation 
 were very nearly uniform. 
 
 Table 19. — Xitrogeu and carbon and fuel values of urine and fecea {respiration experi- 
 ment No. 3). 
 
 tory 
 nnrii- 
 bcr. 
 
 5020 
 
 l'rin« and feces. 
 
 Urino (March 16-17, a. m. to 
 
 «a. m.) 
 
 trine (Marcli 17-18, a. m. to 
 
 6 a. ni.) 
 
 I'rine (.Vlarch 18-19, 6 a. ni. to 
 
 6 a. ni.) 
 
 I'rine (March 19-20, a ni. to 
 
 6 a. m.) 
 
 Urine (Marcli 20-21, 6 a. m. U) 
 
 6 a. m.) 
 
 Total 
 
 Feces (ave,rHgc for 1 day). 
 Total, 5 dayH 
 
 Amount. 
 
 Nitrogen. 
 
 Carbon. 
 
 Fuel 
 
 value per 
 
 gram. 
 
 Total 
 
 fuel 
 
 value. 
 
 Grams, 
 974 
 
 Perct. 
 1.30 
 
 Oraint. 
 12.06 
 
 Per et. 
 0.89 
 
 Grams. 
 8.60 
 
 Calories. 
 0.101 
 
 Calories. 
 98 
 
 1,118 
 
 1.20 
 
 i:i.46 
 
 .89 
 
 9.95 
 
 .101 
 
 113 
 
 1.188 
 
 1.15 
 
 13.61 
 
 .89 
 
 10. £7 
 
 .101 
 
 120 
 
 1,325 
 
 1.04 
 
 13.69 
 
 .89 
 
 11.79 
 
 .101 
 
 134 
 
 1,.520 
 
 1.00 
 
 15.22 
 
 .80 
 
 13.58 
 
 .101 
 
 l.')4 
 
 6, 131 
 16.4 
 81.9 
 
 "li.'ai' 
 
 08.64 
 
 .87 
 
 4.37 
 
 "'4i."94' 
 
 54. 55 
 0.87 
 34. 33 
 
 ""i.iwi 
 
 6 19 
 
 79 
 
 395 
 
 
 
 
 2771— No, 44- 
 
50 
 
 Tlie amount of carbon dioxid produced during the period in the res- 
 piration chamber is shown in Table 20. 
 
 Table 20. — Carbon dioxid pi-ocluced in resjnraiion experiment No. 3. 
 
 
 Period. 
 
 Ventila- 
 tion 
 (volume 
 of air). 
 
 CO2 per liter. 
 
 Total 
 ■weight 
 CU2 ex- 
 haled by 
 subject. 
 
 Total 
 
 Date. 
 
 In incom- 
 ing air. 
 
 In outgo- 
 ing air. 
 
 Given 
 off by 
 subject. 
 
 ■weight C 
 exhaled 
 in COj. 
 
 March 16, 11 a. ip., to 
 March 17, 11 a. ra. 
 
 fll a.m. to 6p. m.- - 
 
 1(3 p.m. to la. n) 
 
 11 a.m. to 7 a. m 
 
 Liters. 
 37, 462 
 41, 560 
 37, 360 
 
 0.57 
 .56 
 .55 
 
 Mg. 
 7.57 
 6.13 
 4.61 
 
 Mg. 
 7.00 
 5 57 
 4.06 
 
 Grams. 
 262.2 
 231.3 
 151.6 
 
 Grams. 
 I 220. 9 
 
 
 ,7 a.m. to Ip. m 
 
 36, 470 
 
 .56 
 
 7.19 
 
 6.63 
 
 f 1 164. 9 
 \ ' 82. 6 
 
 1 
 
 March 17, 11 a. m., to 
 March 18, 11 a. m. 
 
 1 p.m. TO 8 p. m 
 
 <8 p.m. to 3 a. m 
 
 3 a.m. to 9 a. m 
 
 40, 150 
 29, 620 
 27, 470 
 
 .60 
 .57 
 .62 
 
 7.21 
 6.86 
 6.88 
 
 6.61 
 6.29 
 6.26 
 
 265.6 
 186.3 
 171.9 
 
 I 215. 3 
 
 
 ;9 a. m. to 4 p. m 
 
 31, 500 
 
 .61 
 
 9.89 
 
 9.28 
 
 / 1 83. 2 
 \ 1208.2 
 
 1 
 
 March 18, 11 a. m., to 
 March 19, 11 a. m. 
 
 J4 p.m. to 11 p.m... 
 1 11 p. m to 6 a. m . . . 
 
 30, 830 
 30, 330 
 
 .58 
 .63 
 
 9.07 
 5.87 
 
 8.49 
 5.24 
 
 261.9 
 159.0 
 
 I 218. 8 
 
 
 [e a.m. to Ip. m 
 
 30, 700 
 
 .62 
 
 8.51 
 
 7.89 
 
 / 1173.1 
 
 \ 1 69. 2 
 
 272.9 
 
 216. 6 
 
 220.2 
 
 J 
 
 March 19, 11 a. m., to 
 March 20, 11 a. m. 
 
 1 p. m. toSj). m 
 
 <8 p.m. to 3 a. m 
 
 3 a. m. to 10 a. m . . . 
 
 33, 210 
 33, 930 
 33, 820 
 
 .65 
 .57 
 .53 
 
 8.87 
 6.99 
 7.04 
 
 8.22 
 6.42 
 6.51 
 
 \ 222. 9 
 
 March 20, 11 a. m., to 
 March 21, 11 a. m. 
 
 Wo a.m. to 6p.m..- 
 
 ^6 p.m. to 2a. m 
 
 I2 a.m. to 11 a.m... 
 
 37, 060 
 
 40, 990 
 44, 093 
 
 .57 
 
 .56 
 ..52 
 
 8.86 
 
 7.36 
 6.54 
 
 8.29 
 
 6.80 
 6.02 
 
 / 1 38. 4 
 
 1 1268.8 
 
 278.6 
 
 265.5 
 
 i 221. 7 
 
 1 Of the period from 7 a. m. to 1 p. m., March 17, four hours belong to the first and the remainder to 
 the second day of the experiment. 
 
 In like manner each experimental period is made to end at 11 a. m., the amount of COj eliminated in 
 the period in "tvhich the day ends being divided between that day and the next jiroportionately to the 
 time. 
 
 The balance of income and outgo of nitrogen and carbon, as computed 
 from the data given in Tables 18, 19, and 20, is shown in Table 21: 
 
 Table 21.— Balance of income and outgo of nitrogen and carbon {respiration experiment 
 
 No. 3). 
 
 
 Nitrogen. 
 
 Carbon. 
 
 Puel value. 
 
 Date. 
 
 In 
 
 In 
 
 In 
 
 Gain 
 
 ( + ) or 
 
 In 
 
 In 
 
 In 
 
 In res- 
 pira- 
 tory 
 prod- 
 
 Gain 
 (+) or 
 
 Of 
 
 Of 
 
 Of 
 
 
 food. 
 
 urine. 
 
 feces. 
 
 loss 
 
 food. 
 
 urine. 
 
 feces. 
 
 loss 
 
 food. 
 
 urine. 
 
 feces. 
 
 
 
 
 
 
 
 
 
 ucts. 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 Calo- 
 
 Calo- 
 
 Calo- 
 
 March 16-17, 11 
 
 Gms. 
 
 Gms. 
 
 .Gms. 
 
 Gms. 
 
 Gms. 
 
 Gms. 
 
 Gms. 
 
 Gms. 
 
 Gms. 
 
 ries. 
 
 ries. 
 
 ries. 
 
 a.m. to 11 a.m. 
 
 15.3 
 
 12.7 
 
 0.9 
 
 +1.7 
 
 234.3 
 
 8.7 
 
 6.9 
 
 220.9 
 
 — 2.2 
 
 2,645 
 
 98 
 
 79 
 
 March 17-18, 11 
 
 
 
 
 
 
 
 
 
 
 
 
 
 a. m. to 11 a. m. 
 
 15.3 
 
 13.5 
 
 .9 
 
 +0.9 
 
 234.3 
 
 9.9 
 
 6.9 
 
 215.3 
 
 + 2.2 
 
 2,645 
 
 113 
 
 79 
 
 March 18-19, 11 
 
 
 
 
 
 
 
 
 
 
 
 
 
 a. m.toll a. m. 
 
 15. a 
 
 13.6 
 
 .9 
 
 +0.8 
 
 234.3 
 
 10.6 
 
 6.9 
 
 218.8 
 
 — 2.0 
 
 2,645 
 
 120 
 
 79 
 
 March 19-20, 11 
 
 
 
 
 
 
 
 
 
 
 
 
 
 a.m. to 11a. m- 
 
 15. 3 
 
 13.7 
 
 .9 
 
 + 0.7 
 
 234.3 
 
 11.8 
 
 6.9 
 
 222. 9 
 
 — 7.3 
 
 2,645 
 
 134 
 
 79 
 
 March 20-21, 11 
 
 
 
 
 
 
 
 
 
 
 
 
 
 a. m.toll a. m. 
 
 15.3 
 
 15.2 
 
 .9 
 
 —0.8 
 
 234.3 
 
 13.6 
 
 6.9 
 
 221.7 
 
 — 7.9 
 
 2, 645 
 
 154 
 
 79 
 
 Total, 5 days 
 
 76.5 
 
 68.7 
 
 4.5 
 
 +3.3 
 
 1, 171. 5 
 
 54.6 
 
 34.5 
 
 1, 099. 6 
 
 —17.2 
 
 13, 225 
 
 619 
 
 395 
 
51 
 
 The calculated gains and losses of inotein and fat are shown in 
 Table 22 : 
 
 Taiu.k 22. — daiii or loss of protein and fat {respiration experiment Xo. 3). 
 
 Date. 
 
 March 16-17, 11 a. m. to 11 a. m. 
 March 17-18, 11 a. m. to 11 a. m. 
 March 18-19. 11 a. lu. to U a. m. 
 March 19-20, 11 a. m. to 11 a. m. 
 March 20-21, 11 a. m. to 11 a. m. 
 
 Total. 5 days 
 
 Nitrogen 
 gained 
 
 (+) or 
 lest (— ). 
 
 Grams. 
 
 +1.7 
 + 0.9 
 + 0.8 
 + 0.7 
 —0.8 
 
 +3.3 
 
 Protein 
 gained 
 
 ( + ) or 
 lost (-). 
 
 Grama. 
 + 10.6 
 + 5.6 
 + 5.0 
 + 4.4 
 — 5.0 
 
 + 20.6 
 
 Total 
 carbon 
 gained 
 (+) or 
 lost (— ). 
 
 Grams. 
 
 — 2.2 
 
 + 2.2 
 
 — 2.0 
 
 — 7.3 
 
 — 7.9 
 
 -17.2 
 
 I Algeliraic 
 Carbon ini ditt'erence 
 protein between tr- 
 
 ained 
 
 ■(+) or 
 lost (— ). 
 
 Grams. 
 + 5.6 
 + 3.0 
 
 + 2.7 
 + 2.3 
 — 2.7 
 
 + 10.9 
 
 t.al carbon 
 
 and carbon 
 
 in protein 
 
 (=M). 
 
 Grams. 
 
 — 7.8 
 
 — 0.8 
 - 4.7 
 
 — 9.6 
 
 — 5.2 
 
 28.1 
 
 Fat 
 gained 
 
 ( + )or 
 lost (— ) 
 
 (M-- 
 
 0.765K 
 
 Grams. 
 —10.2 
 
 — 1.0 
 
 — 6.1 
 —12.6 
 
 — 6.8 
 
 -36.7 
 
 - RESPIRATION EXPERIMENT No. 4 (DIGESTION EXPERIMENT No. 14). 
 
 The last experiment was more detailed than the jirevious ones and 
 the observations were more thoroughly systematized. The subject 
 was a i)hysicist (A. W. S.), 22 years old, and weighed (without clothing) 
 at the beginning of the experiment 69.1) kilograms (154 pounds). The 
 exi)eriment began with breakfast March 19 and ended with dinner 
 April 4, thus covering sixteen and two-third days and including tifty 
 meals. During the twelve days beginning 3 p. m. March 23 and ending 
 3 p. m. April 4 the subject was in the respiration chamber. The twelve 
 days were divided into five periods, the first of one and five-eighths, 
 the lifth of one and three-eighths, and the others of three days' dura- 
 tion each. The iirst and fifth periods were preliminary and supple- 
 mentary. In these preliminarj^ and supplementary periods thus reck- 
 oned as one the subject did not engage in any muscular or mental 
 work except such reading and very slight physical exercise as were 
 needed to pass away the time comfortably. For convenience in making 
 the calculations of income and outgo, it was assumed that the amounts 
 of ingredients of food and excretory products for the five-eighths 
 and three-eighths days, resiiectively, made up the corresponding pro- 
 jtortions of the total daily amounts. Of course this assumption does not 
 affect the other periods of the exjierimcnt. The second period, of three 
 days duration, w^as devoted to mental labor. The subject engaged for 
 eight hours a day or thereabouts in the active work of either caculating 
 results of previous experiments or studying a German treatise on 
 physics. The mental application was as intense as it could well be 
 made. The tliird period, likewise of three days' duration, was given 
 to nearly absolute rest. During this time the subject avoided muscular 
 and mental exercise so far as possible. During a larger part of the 
 time he n'clined upon the bed. Of course it was impossible to avoid 
 all intellectual activity, but the amount was made as small as practi- 
 cable. The fourth period was one of intense muscular activity. A 
 
52 
 
 pulley was attached to the top of tlie chamber. Over this passed a 
 cord. One end of the cord was attached to a block of iron weighing 
 5.7 kilograms (12.5 x)ounds) ; on the other end was a handle. This pro- 
 vided for active exercise, not only of the arms, but also of the legs and 
 other parts of the body. The whole arrangement was quite similar 
 to some of the forms of apparatus very commonly used for gymnastic 
 exercise. With this the subject worked severely for eight hours on 
 eacli of the three days, so that at the end of each day's work he was 
 thoroughly tired. He perspired very freely during the working hours. 
 This period was followed by the final short period of rest. 
 
 In examining the detailed results of the experiments it was interest- 
 ing to note that whatever had been the occupation during the day a 
 period of G hours' rest was sufficient to bring the elimination of carbon 
 dioxid back to a normal quantity. Even after the large elimination of 
 carbonic acid which accompanied each period of hard muscular work, 
 amounting at times to 500 grams for six hours, the simple return to rest 
 was followed almost immediately by a return to the normal elimination 
 (see Table 27). 
 
 In the case of the elimination of nitrogen in the urine, however, the 
 increase consequent upon hard muscular work or its decrease when the 
 body was in a state of rest did not manifest itself until some hours 
 after the muscular work began or ended (see Table 26). In the calcula- 
 tions for Table 26 a period of six hours was allowed for the lag in the 
 urine. By consulting that table, however, it will be seen that the 
 increase of nitrogen in the urine following the hard work of March 31 
 did not manifest itself until apparently thirty hours later, and did not 
 cease for an equally long period after the close of active exercise on 
 the evening of April 2, during which time the body had been in a 
 state of as complete inactivity as possible. This subject is referred 
 to beyond. 
 
 The character of the food consumed during this experiment is shown 
 in the following daily menu : 
 
 Table 23 — Daily menu, respiration experiment Ho. 4 {digestion experiment No. 14). 
 
 Breakfast. 
 
 Dinner. 
 
 Supper. 
 
 
 Grams. 
 75 
 40 
 120 
 150 
 15 
 20 
 
 
 Grams. 
 96 
 75 
 
 100 
 30 
 
 125 
 
 Milk 
 
 Grams. 
 500 
 
 
 
 
 250 
 
 
 Maslied potatoes 
 
 Butter 
 
 
 
 Milk 
 
 
 Butter 
 
 
 
 
 
 
 
 
 Tables 24 and 25 show the amounts, composition, and fuel values of 
 the food and feces and the coefficients of digestibility for the whole 
 period (sixteen and two-thirds days) and the amount, composition, and 
 fuel value of the food for the period in the respiration chamber (twelve 
 days). 
 
 i 
 
53 
 
 Table 24. — Food eaten and digested during the ivhole experimental period, IGJ days 
 (digestion experiment No. 14). 
 
 Labo- 
 ra- 
 tory 
 
 num- 
 ber. 
 
 2715 
 4249 
 4250 
 2727 
 2726 
 2723 
 2728 
 2725 
 2709 
 2722 
 
 Kind of food. 
 
 Beef, fried 
 
 Butter 
 
 Milk 
 
 Kri'Md, wliit^' 
 
 Hre.id, brown 
 
 Oatmeal 
 
 Hean.s 
 
 Potatoes, boiled 
 
 Apples 
 
 Sugar 
 
 Feces 
 
 Total. 
 
 Amount digested. 
 Fuel value urea 
 
 Not amount digested. 
 Per cent digested 
 
 "Weight 
 
 for 
 experi- 
 ment. 
 
 Grams. 
 1,654 
 
 7C5 
 10, 0(10 
 2, 550 
 4, 000 
 
 680 
 2, 040 
 1,700 
 2,125 
 
 340 
 
 Total 
 organic 
 matter. 
 
 Grams. 
 
 738 
 
 673 
 
 1,384 
 
 1,016 
 
 2, 022 
 
 609 
 
 516 
 
 393 
 
 279 
 
 340 
 
 8,570 
 330 
 
 8,240 
 
 Protein 
 (NX6.25). 
 
 Grams. 
 506 
 8 
 351 
 235 
 232 
 117 
 141 
 42 
 
 1,697 
 147 
 
 1,550 
 
 Fat. 
 
 Grams. 
 
 172 
 
 665 
 
 445 
 
 35 
 
 46 
 
 48 
 
 7 
 
 1 
 
 4 
 
 1,423 
 58 
 
 1, 365 
 
 Carbo- 
 hydrates. 
 
 Grams. 
 
 588 
 I, 340 
 1,744 
 444 
 368 
 350 
 270 
 340 
 
 5, 450 
 125 
 
 5,325 
 
 Fuel 
 value, 
 deter- 
 mined. 
 
 Galori<'K. 
 4, 803 
 
 6, 249 
 8, 4.59 
 
 7, 375 
 y, 220 
 2. 998 
 2, 405 
 1,681 
 1, 102 
 1, 35(> 
 
 45, 708 
 2, 049 
 
 43, C,y.) 
 1,347 
 
 42, 312 
 92.6 
 
 Tablk 25. — Food eaten during the period in the respiration chamber, 12 days {respiration 
 
 experiment No. 4). 
 
 Labo- 
 ra- 
 tory 
 num- 
 ber. 
 
 2715 
 4249 
 4250 
 2727 
 2726 
 2723 
 2728 
 2725 
 2709 
 2722 
 
 Kind of food. 
 
 Twelve days, 36 meals. 
 
 Beef, fried 
 
 Butter 
 
 Milk 
 
 Bread, white . 
 Brea<l, brown. 
 
 Oatmeal 
 
 Beans 
 
 Potatoes 
 
 Apples 
 
 Sugar 
 
 Total. 
 
 Weight 
 per day. 
 
 Grams. 
 
 90 
 
 45 
 650 
 1.50 
 250 
 
 40 
 120 
 100 
 125 
 
 20 
 
 Xitro- 
 
 G rains. 
 
 5.28 
 
 .08 
 
 3.45 
 
 2.22 
 
 2.32 
 
 1.10 
 
 1.32 
 
 .40 
 
 .05 
 
 Carbon. 
 
 16.22 
 
 Grams. 
 
 22. 33 
 
 30. 08 
 
 39.06 
 
 41.73 
 
 55.67 
 
 16.46 
 
 13.64 
 
 9.77 
 
 6.99 
 
 8.41 
 
 244. 14 
 
 Protein. 
 
 Grams. 
 
 33.0 
 
 .5 
 
 21.5 
 
 13.8 
 
 14.5 
 
 6.9 
 
 8.3 
 
 2.5 
 
 .3 
 
 101.3 
 
 Fat. 
 
 Grams. 
 
 10.0 
 
 39.1 
 
 27.3 
 
 2.0 
 
 2.9 
 
 2.8 
 
 .4 
 
 .1 
 
 .2 
 
 84.8 
 
 Carbo- 
 hy- 
 drates. 
 
 Grams. 
 
 36.1 
 79.2 
 109. 
 20. 1 
 21.6 
 20.6 
 15. 9 
 20.0 
 
 328.5 
 
 Fuel values. 
 
 Deter- 
 mined. 
 
 Calories. 
 280 
 368 
 519 
 434 
 576 
 170 
 141 
 99 
 08 
 80 
 
 Calcu- 
 lated. 
 
 2,741 
 
 Calories. 
 
 273 
 
 367 
 
 520 
 
 420 
 
 553 
 
 171 
 
 138 
 
 99 
 
 69 
 
 82 
 
 2, 692 
 
 Table 20 gives the amount of urine and feces excreted during the 
 period in the respiration chamber and the nitrogen and carbon content 
 and fuel value of each. 
 
 Taislk 26. — Nitrogen and carbon in urine and feces (respiration experiment No. 4). 
 
 Lab- 
 ora- 
 
 
 a 
 
 
 
 Fuel 
 value 
 
 Total 
 
 
 lorj' 
 
 Urine and feezes. 
 
 S 
 
 Nitrogen. 
 
 (Jarbon. 
 
 fuel 
 
 Kemarks. 
 
 mini' 
 
 
 
 
 
 
 value. 
 
 
 U:t. 
 
 
 < 
 
 
 
 gram. 
 
 
 
 
 
 Per 
 
 
 Per 
 
 
 Cal- 
 
 Cal- 
 
 
 
 
 Gm,s. 
 
 cent. 
 
 Gms. 
 
 cent. 
 
 Gms. 
 
 ories. 
 
 ories. 
 
 
 
 rrrrine (March 23-24, 9 p. m. to 
 ) 12 m.). 
 
 590 
 
 1..53 
 
 9.12 
 
 0.99 
 
 5.90 
 
 0.113 
 
 67 
 
 j Prelim inary 
 
 .0022 
 
 
 
 
 
 
 
 
 > period, no 
 
 llJrini^ (.March 24-25, 12 in. to 
 
 772 
 
 1.83 
 
 14.09 
 
 .90 
 
 7.64 
 
 .113 
 
 87 
 
 ) work. 
 
 
 1 12 m.). 
 
 
 
 
 
 
 
 
 
 
 Irim- (March 25-2(i, 12 m. Ut 
 
 815 
 
 1.61 
 
 13. 12 
 
 .72 
 
 5.87 
 
 .083 
 
 «8 
 
 
 
 12 ni). 
 
 
 
 
 
 
 
 
 
 
 I'riiie (M;ircli 26 27, 12 in. to 
 
 1,230 
 
 1.11 
 
 13.71 
 
 .72 
 
 8,86 
 
 .083 
 
 102 
 
 VMciilal work. 
 
 5<i2:i 
 
 12 111). 
 
 
 
 
 
 
 
 
 
 
 -L'riiii- (.March 27 28, 12 in. to 
 
 1,600 
 
 .79 
 
 12. (i4 
 
 .72 
 
 11.52 
 
 . 083 
 
 133 
 
 
 
 I Viiu.i. 
 
 
 
 
 
 
 
 
 
54 
 
 
 Table 26. — Nitrogen 
 
 and carbon 
 
 in urine and feces- 
 
 —Continued. 
 
 Lab- 
 ora- 
 tory 
 num- 
 ber. 
 
 Urine and feces. 
 
 
 o 
 
 1 
 
 Nitrogen. 
 
 Carbon. 
 
 Fuel 
 
 value 
 
 per 
 
 gram. 
 
 Total 
 fuel 
 value. 
 
 Kemarks. 
 
 5024 
 
 5025 
 502(J 
 
 rUrine (March 28-29, 12 ni. to 
 12 m.). 
 
 Urine (March 29-30, 12 m. to 
 12 ni.). 
 
 Urine (March 30-31, 12 m. to 
 
 , 12 m.). 
 
 fUrine (March 31-April 1, 12 m. 
 
 1 to 12 ra.). 
 
 lUrine(April 1-2, 12m. tol2m.K. 
 
 [Urine (April 2-3, 12m. to 12m.) . . 
 
 rUrine (April 3-4, 12ni. to 12 m.) . . 
 1 Urine (April 4, 12 m. to 9 p. m.) . . 
 
 Total 
 
 Oms. 
 1,713 
 
 L107 
 
 1,422 
 
 662 
 
 841 
 
 798 
 
 1,529 
 822 
 
 Per 
 cent. 
 0.70 
 
 1.12 
 
 .92 
 
 L77 
 
 1.95 
 L79 
 
 L05 
 .65 
 
 0ms. 
 11.90 
 
 12. 40 
 
 13.08 
 
 11.68 
 
 16.40 
 14.29 
 
 16.13 
 5.34 
 
 Per 
 
 cent. 
 0.76 
 
 .76 
 
 .76 
 
 1.31 
 
 1.31 
 L31 
 
 .73 
 .73 
 
 Gms. 
 13. 02 
 
 8.41 
 
 10.81 
 
 8.67 
 
 11.02 
 10.45 
 
 11.16 
 6.00 
 
 Cal- 
 ories. 
 0.089 
 
 .089 
 
 .089 
 
 .151 
 
 .151 
 
 .151 
 
 .055 
 .055 
 
 Cal- 
 ories. 
 152 
 
 99 
 
 126 
 
 100 
 
 127 
 121 
 
 84 
 45 
 
 .No work. 
 
 1 Muscular 
 ( work. 
 
 (S upplemen- 
 < tary ]ieriod, 
 [ no work. 
 
 
 13, 907 
 
 25.4 
 
 304. 8 
 
 5.46 
 
 163. 90 
 
 L39 
 
 16.64 
 
 4i."40' 
 
 119. 33 
 10.52 
 126. 20 
 
 4.723' 
 
 1,311 
 
 120 
 
 1,440 
 
 
 2761 
 
 Pece.s (average for 1 day ) 
 
 Total 
 
 
 
 
 
 
 
 The amount of carbon dioxid produced during- the period in the 
 respiration chamber is shown in Table 27. 
 
 Table 27. — Carbon dioxid produced in respiration experiment No. 4. 
 
 Date. 
 
 Period. 
 
 Ventila- 
 tion 
 (volume 
 of air). 
 
 COj per liter. 
 
 In incom- 
 ing air. 
 
 In outgo- 
 ing air. 
 
 Given 
 
 off by 
 
 subject. 
 
 Total 
 weight 
 COj ex- 
 haled by 
 subject. 
 
 Total 
 
 weight C 
 
 exhaled 
 
 in CO2. 
 
 March 23, 3 p. m., to 
 March 24, 6 a. m 
 
 to I 
 
 March 24, 6 a. m., to 
 March 25, 6 a. m. 
 
 March 25, 6 a. m., to 
 March 26, 6 a. m. 
 
 March 26, 6 a. m., to 
 March 27, a. m. 
 
 March 27, 6 a. m., to 
 March 28, 6 a. m. 
 
 March 28, 6 a. m., to 
 March 29, 6 a. m. 
 
 March 29, 6 a. m., to 
 March 30, 6 a. m. 
 
 March 30, 6 a. in., to 
 March 31, 6 a. m. 
 
 March 31, 6 a. m.. to 
 April 1, 6 a. m. 
 
 3 p.m. to 9 p.m. 
 9 p. m. to 3 a. m. 
 
 3 a.m. to 9 a.m. 
 
 9 a.m. 
 3 p.m. 
 9 p.m. 
 
 3 a.m. to 9 a.m. 
 
 . to 3 p.m. 
 .to 9 p. m. 
 .to 3 a.m. 
 
 • to 3 p.m. 
 .to 9 p.m. 
 .to 3 a. m. 
 
 9 a. m 
 3 p. m 
 9p. m 
 
 3 a.m. to 9 a. m 
 
 9 a.m. 
 3 p. m. 
 9 p. m. 
 
 3 a.m. 
 
 9 a.m. 
 3 p.m. 
 9 p. 
 
 3 a.m. to 9 a.m... 
 
 to 3 p.m. 
 to 9 p. m . 
 to 3 a. ni- 
 
 . to 3 p.m. 
 . to 9 p. m . 
 . to 3 a.m. 
 
 .to 3 p.m. 
 .to 9 p.m. 
 . to 3 a. m . 
 
 9 a. m. 1 
 3 p. m. 
 9 p.m. 
 
 3 a. m. to 9 a. m. 
 
 9 a.m. 
 3 p.m. 
 9 p.m. 
 
 3 a.m. 
 
 9 a.m. 
 3 p. m. 
 9 p.m. 
 
 3 a. lu. 
 
 9 a.m. 
 3 p.m. 
 9 p.m. 
 
 3 a.m. 
 
 to 3 p.m. 
 to9 p. m. 
 to 3 a.m. 
 
 to 3 p. m. 
 to 9 p.m. 
 to 3 a.m. 
 
 to 3 p. m . 
 to 9 p. m. 
 to 3 a. m . 
 
 Liters. 
 
 21, 840 
 23, 348 
 
 23, 606 
 
 20, 962 
 21,420 
 
 22, 288 
 
 21,370 
 
 21, .350 
 21,970 
 21,060 
 
 21, 370 
 
 21, 240 
 22,110 
 
 20, 760 
 
 21, 470 
 
 20, 760 
 21,780 
 22, 190 
 
 21,010 
 
 20, 600 
 21,220 
 
 21, 520 
 
 20, 350 
 
 20, 050 
 
 21, 290 
 20, 790 
 
 20, 350 
 
 21, 320 
 21, 290 
 21, 976 
 
 20, 354 
 
 21, 040 
 21,240 
 20, 750 
 
 20, 240 
 
 Mg. 
 0.62 
 .59 
 
 .58 
 .59 
 .57 
 
 .56 
 .59 
 .56 
 
 .56 
 .57 
 .55 
 
 .58 
 .60 
 .57 
 
 .63 
 .59 
 .55 
 
 .56 
 
 .58 
 .60 
 .61 
 
 .58 
 .61 
 .58 
 
 Mg. 
 10.48 
 9.42 
 
 12.76 
 11.89 
 9.05 
 
 12.77 
 11.96 
 10.34 
 
 8.71 
 
 12.28 
 
 11.44 
 
 9.47 
 
 10.96 
 
 11.05 
 
 9.05 
 
 9.01 
 
 11.32 
 12.52 
 11.31 
 
 12.30 
 11.60 
 9.51 
 
 12.20 
 10.72 
 10.88 
 
 21.09 
 20.37 
 11.20 
 
 Mg. 
 9.86 
 8.83 
 
 12.18 
 11.30 
 8.48 
 
 8.73 
 
 12.22 
 11. 36 
 9.72 
 
 11.72 
 10.85 
 8.91 
 
 10.40 
 10.48 
 8.50 
 
 8.45 
 
 10.74 
 11.92 
 10.74 
 
 8.64 
 
 n.67 
 
 11.01 
 
 8.96 
 
 11.62 
 10.12 
 10.27 
 
 10.90 
 
 20.51 
 19.76 
 10.62 
 
 9.22 
 
 Orams. 
 214.9 
 206.3 
 189.3 
 189.3 
 255.2 
 242.2 
 189.1 
 193.2 
 193.3 
 260.8 
 249.6 
 204.8 
 '87.3 
 187.3 
 248.9 
 239.9 
 184.9 
 188.2 
 '88.1 
 215.8 
 228.2 
 188.7 
 
 221.4 
 252.9 
 23L2 
 187.9 
 188.0 
 240.9 
 234.5 
 186.2 
 19L7 
 19L7 
 247.8 
 215.5 
 225.8 
 1 110. 9 
 1 110. 9 
 431.6 
 419.6 
 220.6 
 '93.3 
 '93.4 
 
 rams. 
 139. 2 
 
 237.0 
 
 244.3 
 
 220.7 
 
 240.6 
 
 243.2 
 
 348.0 
 
 'Each experimental day ended at 6 a. m. ; therefore the amount of CO-^ in the period from 3 a. m. to 
 9 a. m. is divided equally between the two days. 
 
55 
 
 Tablk 27. — Carbon diuxid jfioduced in resjy'iration experiment No. 4 — Continued. 
 
 Date. 
 
 Period. 
 
 i 9 
 April 1. 6 a. ni., to , ., 
 
 April "J, 6 .a. iii 
 
 a. m 
 p. m 
 p. lU 
 
 to 3 
 to 9 
 to 3 
 
 p.m. 
 p. ni. 
 ii. 111. 
 
 April 2. 6 a. m., to 
 April 3, 6 a. m. 
 
 .\pril 3. 6 a. in., to 
 Ajdil 4. a. III. 
 
 April 4, 6 a. ni., to ( 
 April 4, 3 i>. lu. \ 
 
 9] 
 
 3 a. III. to!), a. in. 
 
 9: 
 
 3] 
 
 9] 
 
 3 a. ui. to 9 a.m.. 
 
 I a. III. 
 I p. Ill, 
 I p. Ill, 
 
 t..3 
 to 9 
 to 3 
 
 11.111. 
 a. III. 
 
 a. m. 
 p. m, 
 ]i. Ill 
 
 to 3 
 to 9 
 to3 
 
 3 a.m. to 9 
 9 a. m. to 3 
 
 p. Ill . 
 p. 111. 
 a. 111. 
 
 a. III. 
 
 p. 111. 
 
 Ventila- 
 tion 
 (volume 
 of air). 
 
 CO2 per liter. 
 
 lAtert. 
 21. 290 
 21,330 
 20, 890 
 
 19, 390 
 
 19, 972 
 21.400 
 21,941 
 
 20, 820 
 
 20, fi86 
 21.360 
 21, 125 
 
 20, 57:) 
 
 21,268 
 
 In incom- 
 ing air. 
 
 (1.65 
 .63 
 .62 
 
 .71 
 
 .61 
 .65 
 
 .83 
 
 1.55 
 
 .83 
 
 .87 
 1.23 
 
 1.94 
 
 .57 
 
 In outgo- 
 ing air. 
 
 Given 
 
 oft" by 
 
 subject. 
 
 Mg. 
 24. 18 
 22. 73 
 11.36 
 
 10.94 
 
 23.92 
 24.62 
 11. 39 
 
 11.86 
 13.40 
 11.29 
 
 10.86 
 
 12.44 
 
 Mg. 
 23.53 
 22. 10 
 10.74 
 
 10.23 
 
 23. 31 
 23. 97 
 10. 56 
 
 8.72 
 
 11.03 
 12.53 
 10.06 
 
 8.92 
 
 11.87 
 
 Total 
 weight 
 COj ex- 
 haled by 
 subject. 
 
 Total 
 weight C 
 exhaled 
 in CO.,. 
 
 Grains. 
 500.9 
 471.4 
 246.0 
 ' 99. 1 
 ' 99. 2 
 465.6 
 512.9 
 231.6 
 ■90.8 
 190.8 \\ 
 228.2 ' 
 266. S \ 
 212.4 
 '91.8 J 
 '91.8 \ 
 252.5 / 
 
 (Ira ins. 
 
 ' Each experimental day eniled at 6 a.m.; therefore the amount of CO^ in the period from 3 a. ni. to 
 9 a. m. in divided eijuall.y between the two days. 
 
 The balance of income and outgo of nitrogen and carbon made up 
 from data given in Tables 25, 20, and 27 is shown in the following 
 table : 
 
 T.vuLK 28. — Ualancc of income and outijo of nitrogen and carbon (renpiralion experiment 
 
 ' No. 4). 
 
 Date. 
 
 March 23-24, 9 
 
 p. III. to 12 III... 
 March 24-25, 12 
 
 III. to 12ui 
 
 ilaich 2.5-26, 12 
 
 III. to 12 m 
 
 March 26-27, 12 
 
 ui. to 12 m.... 
 Man b 27-28, 12 
 
 ni. tci 12 m 
 
 March 28-29, 12 
 
 m. to 12m 
 
 March 29-30, 12 
 
 ni. to 12m 
 
 ilarch 30-31, 12 
 
 m. to 12 m 
 
 March 31-April 
 
 1. 12 III. to 12 m 
 April 1-2, 12 m. 
 
 to 12 m 
 
 April 2-3, 12m. 
 
 to 1 2 m 
 
 April 3-4, 12m. 
 
 to 12 III 
 
 A pril 4. 12 m. to 
 
 9 p. lu 
 
 Nitrogen. 
 
 In 
 food. 
 
 ms. 
 10.1 
 
 16.2 
 
 16.2 
 
 16.2 
 
 16.2 
 
 16.2 
 
 16.2 
 
 16.2 
 
 16.2 
 
 16.2 
 
 16.2 
 
 16.2 
 
 6.1 
 
 In In 
 uriue.i feces- 
 
 Total,12(lay8l94.4 
 
 Gmn. 
 9.1 
 
 14.1 
 
 13.1 
 
 13.7 
 
 12.6 
 
 11.9 
 
 12.4 
 
 13.1 
 
 11.7 
 
 16.4 
 
 14.3 
 
 16.1 
 
 5.4 
 
 Gms. Gms. 
 
 0.9 I -f 0.1 
 
 I 1.4 ! -fO.7 
 
 1.4 ' -fl.7 
 
 I 1.4 -hl.l 
 
 I 1.4-1-2.2 
 
 ' 1.4 -1-2.9 
 
 1.4 +2.4 
 
 1.4 +1.7 
 
 1.4 I +3.1 
 
 1.4 —1.6 
 
 1.4 I +0.5 
 
 1.4 —1.3 
 
 .5 1^0.2 
 
 Carbon. 
 
 In I In 
 food, iuriue. 
 
 103.9 
 
 Gramg. 
 152. 6 
 
 244.1 
 
 244.1 
 
 244.1 
 
 244.1 
 
 244.1 
 
 244.1 
 
 244.1 
 
 244.1 
 
 244.1 
 
 244.1 
 
 244.1 
 
 91.5 
 
 16.8 +13.7 ,2,929.2 
 
 Gms. 
 5.9 
 
 7.6 
 
 5.9 
 
 8.9 
 
 11.5 
 
 13.0 
 
 8.4 
 
 10.8 
 
 8.7 
 
 11.0 
 
 10.4 
 
 11.2 
 
 6.0 
 
 119.3 
 
 
 In res- 
 
 In 
 feces. 
 
 pira- 
 tory 
 prod- 
 ucts. 
 
 Gms. 
 6.6 
 
 Grams. 
 139. 2 
 
 10 5 
 
 237.0 
 
 10.5 
 
 244.3 
 
 10.5 
 
 231.6 
 
 10.5 
 
 220. 7 
 
 10.5 
 
 240.6 
 
 10.5 
 
 229.4 
 
 10.5 
 
 243.2 
 
 10.5 
 
 348.0 
 
 10.5 
 
 384.8 
 
 10.5 
 
 381.8 
 
 10.5 
 
 242.7 
 
 3.9 
 
 93.9 
 
 120.0 
 
 3, Zil. 2 
 
 Gain 
 
 ( + )or 
 loss 
 
 (-)■ 
 
 Grams. 
 
 + 0.9 
 
 — 11.0 
 
 — 16.6 
 
 — 6.9 
 + 1.4 
 
 — 20.0 
 4.2 
 
 — 20.4 
 123.1 
 
 —162. 2 
 —158. 6 
 
 — 20.3 
 
 — 12.3 
 
 Fuel value. 
 
 -553.3 
 
 Of 
 food. 
 
 Of 
 urine. 
 
 Calo- 
 ries. 
 1, 713 
 
 Calo- 
 ries. 
 67 
 
 2,741 
 
 87 
 
 2,741 
 
 68 
 
 2,741 
 
 102 
 
 2,741 
 
 133 
 
 2,741 
 
 152 
 
 2,741 
 
 99 
 
 2,741 
 
 126 
 
 2,741 
 
 100 
 
 2,741 
 
 127 
 
 2,741 
 
 121 
 
 2,741 
 
 84 
 
 1,028 
 
 45 
 
 32, 892 
 
 1,311 1 
 
 Of 
 feces. 
 
 Calo- 
 
 riei. 
 
 75 
 
 120 
 
 120 
 
 120 
 
 120 
 
 120 
 
 120 
 
 120 
 
 120 
 
 120 
 
 120 
 
 120 
 
 45 
 
 1,440 
 
56 
 
 The calculated gains and losses of protein and fat are shown in the 
 following table : 
 
 Table 29. — Gain or loss of protein and fat {respiration experiment No. 4). 
 
 Date. 
 
 Nitrogen 
 gained 
 
 (+)or 
 lost (— ). 
 
 Protein 
 gained 
 ( + ) or 
 
 lost (— ). 
 
 Total 
 carbon 
 gained 
 ( + ) or 
 lost (— ). 
 
 Carbon in 
 
 protein 
 
 gained 
 
 ( + ) or 
 
 lost (— ). 
 
 Algebraic dif- 
 ference be- 
 tween total 
 
 carbon 
 
 and carbon 
 
 in protein 
 
 (=M). 
 
 Fat 
 gained 
 (+)or 
 lost (— ) 
 (M-j- 
 0.765). 
 
 March 23-24,9 p. m. to 12 m 
 
 Or anas. 
 ■+0.1 
 +0.7 
 + 1.7 
 + 1.1 
 +2.2 
 + 2.9 
 + 2.4 
 + 1.7 
 + 3.1 
 —1.6 
 + 0.5 
 —1.3 
 +0.2 
 
 Grams. 
 + 0.6 
 
 + 4.4 
 + 10.6 
 + 6.9 
 +13.8 
 + 18.1 
 +15.0 
 + 10.6 
 + 19.4 
 —10.0 
 + 3.1 
 — 8.1 
 + 1.2 
 
 Grams. 
 + 0.9 
 
 — 11.0 
 
 — 16.6 
 
 — 6.9 
 + 1.4 
 
 — 20.0 
 
 — 4.2 
 
 — 20.4 
 
 — 123.1 
 —162. 2 
 —158. 6 
 
 — 20.3 
 
 — 12.3 
 
 Grams. 
 + 0.3 
 + 2.3 
 -1- 5.6 
 + 3.7 
 + 7.3 
 + 9.6 
 + 8.i 
 + 5.6 
 +10.3 
 
 — 5.3 
 + 1.6 
 
 — 4.3 
 + 0.6 
 
 Grams. 
 + 0.6 
 
 — 13.3 
 
 — 22.2 
 
 — 10. 6 
 
 — 5.9 
 
 — 29.6 
 
 — 12.2 
 
 — 26.0 
 —133. 4 
 —156. 9 
 —160. 2 
 
 — ICO 
 
 — 12.9 
 
 Grams. 
 + 0.8 
 17 4 
 
 March 24 25 12 ni to 12 lu 
 
 March 25 26 12 m. to 12 m 
 
 29 
 
 March 26 27 12 m. to 12 m 
 
 13 8 
 
 March 27 28 12 m. to 12 m 
 
 7 7 
 
 Marcli 28 29 12 m. to 12 m 
 
 38 7 
 
 March 29-30, 12 m. to 12 ra 
 
 March 30 31 12 m. to 12 m 
 
 — 15.9 
 34 9 
 
 March 31-April 1, 12 m. to 12 m 
 
 April 1 2, 12 m. to 12 m 
 
 —174.4 
 205 1 
 
 April 2 3, 12 m. to 12 m 
 
 209 4 
 
 April 3-4, 12 m. to 12 m 
 
 20. 9 
 
 April 4, 12 m. to 9 p. m 
 
 16.9 
 
 
 
 Total, 12 days 
 
 +13.7 
 
 + 85.6 
 
 —553. 3 
 
 +45.3 
 
 —598. 6 789 4 
 
 
 
 
 DISCUSSION OF RESULTS. 
 
 VENTILATION AND PRODUCTION OF CARBON DIOXID. 
 
 The observations regarding ventilation and the eifects of the presence 
 of carbonic acid in large quantities are of decided interest. The incom- 
 ing air, which was ordinary fresh air from the outside of the building, 
 contained on the average from 0.5 to 0.6 of a milligram of carbon 
 dioxid per liter; in the outgoing air the amount of carbon dioxid aver- 
 aged about 11 milligrams per liter, though the variations from this 
 amount were considerable. In the last experiment, especially, the dif- 
 ferences in bodily activity in the different i:»eriods were very large, and 
 the differences in carbon dioxid exhalation were correspondingly great. 
 The results are epitomized in Table 30, which shows the quantities of 
 air supplied and carbon dioxid jDroduced in each of the four experi- 
 ments : 
 
 Table 30. — Amount of carbon dioxid produced in the respiration apparatus. 
 
 Experi- 
 ment 
 num- 
 ber. 
 
 Subject. 
 
 Occupation. 
 
 Dura- 
 tion of 
 experi- 
 ment. 
 
 Air 
 sup- 
 plied 
 per 
 miuute. 
 
 Amounts of CO2 per liter 
 in outgoing air. 
 
 Average 
 amount 
 of CO, 
 given off 
 in 24 
 hours. 
 
 Mini- 
 mum. 
 
 Maxi- 
 mum. 
 
 Aver- 
 age. 
 
 1 
 
 Janitor (E. 0.) 
 
 do 
 
 Eest 
 
 Days. 
 
 2i 
 
 2i 
 5 
 
 1| 
 3 
 3 
 3 
 
 IJ 
 
 Liters. 
 49 
 50 
 
 75 
 
 55 
 55 
 55 
 55 
 55 
 
 Mg. 
 8.0 
 8.1 
 4.6 
 
 8.1 
 
 8.7 
 9.0 
 9.9 
 10.9 
 
 Mg. 
 13.4 
 12.7 
 9.9 
 
 12.8 
 12.8 
 12.5 
 24.6 
 13.4 
 
 M<i. 
 11.0 
 10.4 
 
 7.4 
 
 10.2 
 10.5 
 10.9 
 16.9 
 11.8 
 
 Grams. 
 778 B 
 
 2 
 
 ... do 
 
 794 6 
 
 3 
 4 
 
 Chemist (O.E.T.) 
 
 Physicist (A.W. S.) .. 
 Average, 12 days 
 
 Light mental 
 work. 
 
 (•Pest 
 
 Mental work 
 
 Rest 
 
 Muscular work . 
 Kest 
 
 806. 4 
 
 848.9 
 
 851.5 
 
 871.7 
 
 1,362.3 
 
 897.7 
 
 
 
 
 
 12 .^.'i 1 8- 1 
 
 24.6 
 
 12.1 
 
 989.2 
 
 
 
 
 
 
 
 
57 
 
 The table sliows that the quantity of carbou dioxid in the incoming 
 air was normal, ranging from 0.55 to ().6() milligrams per liter. The 
 ventilation in experiments Nos. 1 and 2 was at the rate of about 50 
 liters of air per minute; the carbon dioxid in the outgoing air varied 
 from 8 to 13.4 and averaged 10.7 milligrams per liter. 
 
 In experiment No. 3, Avith an average ventilation of 75 liters of air 
 per minute, the range of carbon dioxid in the air was from 4.G to 9.0 
 milligrams per liter and the average 7.4 milligrams per liter. The 
 smaller qiumtity of carbon dioxid in the air as compared with experi- 
 ments !Nos. 1 and 2 was due to the larger ventilation, since the average 
 weight of carbon dioxid given off in twenty-four hours was 84.S.9 grams 
 as compared with 778.0 grams in experiment No. 1 and 794.0 in experi- 
 ment No. 2. In these experiments the subject was either at rest or 
 engaged in light mental work or reading. 
 
 Experiment No. 4 is of much more interest in this connection, since 
 the differences in mental and physical exercise were much wider. 
 During the lirst and fifth periods of one and five-eighths and one and 
 three-eighths days, res[)ectively, the subject was at rest. During the 
 second period, which lasted three days, he was engaged in rather severe 
 mental work. The third period was one of as nearly absolute rest as was 
 l)racticable. In the fourth i)eriod the subject was engaged in severe 
 muscular work for eight hours per day. The rate of ventilation was 
 55 liters i^er minute. The temperature of the air in the chamber was 
 generally from 19° to 20^' C, though it fell at times to 17° and rose 
 during the periods of hard muscular work to 22°. 
 
 The weight of carbon dioxid given oft' in twenty- four hours ranged 
 from about 850 to 900 grams for the days at rest and was no larger with 
 mental work, but averaged over 1,300 grams for the days of muscular 
 work. During two periods of six hours each of hard muscular work 
 the elimination of carbon dioxid reached 513 and 501 grams, respec- 
 tively. During the night, or sleeping period, the exhalation of carbou 
 dioxid was singularly constant irrespective of the day's occupation. It 
 amounted to 175 grams in six hours, with but slight variation from that 
 figure.' 
 
 The weight of carbon dioxid in the outgoing air during the periods 
 of rest and mental work ranged from 8.1 to 13.4 milligrams per liter, 
 but aveiaged not far from 11 milligrams per liter. During the i)eriod 
 of muscular work, however, the range was from 9.9 milligranis per liter 
 in the hours of rest, e. g., at night, to 24.0 milligrams per liter in the 
 hours of severe work. 
 
 Authorities on ventilation commonly estimate the maximum of carbon 
 dioxid pcr(nis.sil)lein the air of inhabited rooms atone part i)ei' thousan*! 
 by volume, which corresjtonds to about 1.97 milligrams of carbon dioxid 
 
 'Fr»r rcc«iit obscrviitioiis of thn vnriatioiiB hi tlio amount of (^arhon dioxid 
 
 (-,\(vvU*\ duriiifj H]it'-]}\ufi and vvakiiifj and under varionH coiiilitioiiH of work and 
 rcHt, Hci- invcHti^jatiiinH liy Sond<^ii and Tif^iTHlfdl ('Skainl. Arrli. I'liyniol., <! (l«l)r»), 
 NoM. l-;j, pp. 1-221; al)tttia(;t<d in i;xp< rinuiit Station Iv'nconl H, p. L'lL'j. 
 
58 
 
 per liter. It will be observed that the amounts of carbon dioxid in the 
 air itt the respiration chamber during these experiments was from 8 to 
 25 milligrams per liter, and averaged 10 to 12 milligrams per liter. In 
 other words, the subjects of these experiments lived constantly in an 
 atmosphere containing from five to six times the amount of carbon dioxid 
 in the standard just referred to. In experiment No. 1 the carbon dioxid 
 rose to nearly tliirteen times the amount in the standard. 
 
 The interesting fact in this connection is that no one of the sub- 
 jects appeared to experience any inconvenience whatever from either 
 these large amounts of carbon dioxid or from any other products of 
 exhalation. 
 
 The subject who remained in the apparatus during the five days of 
 the third experiment was as comfortable in every way, according to his 
 repeated statements both during the experiment and afterwards, as if 
 he had been in a room supi^lied with a larger amount of air. Even 
 in the fourth experiment the subject was not aware of the least incon- 
 venience or discomfort during the twelve days of his sojourn in the 
 chamber. 
 
 It maybe added that these results are in accord with the late experi- 
 ments by Billings, Mitchell, and Bergey,^ which imply that the discom- 
 fort experienced in poorly ventilated rooms is not due to the excess 
 of carbon dioxid. It seems probable, however, that one cause of the 
 discomfort felt in badly ventilated rooms occupied by a number of people 
 may be the large amount of moisture which accumulates in the air, while 
 at the same time the temperature rises. Some of the observations 
 made in the experiments above described accord with this hypothesis.^ 
 
 In anticipation of a special treatment of this phase of the experiments 
 in another place, further discussion is omitted here. 
 
 NUTRIENTS AND FUEL VALUES. 
 
 The nutrients and fuel values of the food eaten and digested in the 
 four experiments are briefly summarized in the following table: 
 
 Table 31. — Total and digested nutrients and fuel value of daily food in the four respiration 
 
 experiments. 
 
 Exper- 
 iment 
 num- 
 ber. 
 
 Subject. 
 
 Dura- 
 
 In total food. 
 
 In digested food. 
 
 tion 
 of ex- 
 peri- 
 ment. 
 
 Pro- 
 tein. 
 
 Fat. 
 
 Carbo- 
 hy- 
 drates. 
 
 Fuel 
 value, 
 deter- 
 mined. 
 
 Pro- 
 tein. 
 
 Fat. 
 
 Carbo- 
 hy- 
 drates. 
 
 Fuel 
 
 value, 
 
 deter- 
 
 mined.a 
 
 1 
 2 
 3 
 
 4 
 
 Janitor (E. 0.) 
 
 ..-.do 
 
 Chemi8t(0.F. T.).. 
 Physicist (A.W. S.) 
 
 Days. 
 
 I' 
 
 12 
 
 Grams. 
 142 
 120 
 96 
 101 
 
 Grams. 
 126 
 112 
 73 
 85 
 
 Grams. 
 296 
 281 
 338 
 329 
 
 Cal- 
 ories. 
 3,230 
 2,925 
 2,645 
 2,740 
 
 Grams. 
 
 136 
 
 110 
 
 90 
 
 93 
 
 Grams. 
 
 123 
 
 109 
 
 69 
 
 62 
 
 Grams. 
 
 290 
 277 
 331 
 321 
 
 Cal- 
 ories. 
 2, 970 
 2,650 
 2,460 
 2,510 
 
 a Fuel value of total food less that of feces and urine. 
 
 ' On the composition of expired air and its eifect on animal life. Smithsonian Con- 
 tributions to Knowledge, Vol. XXIX (No. 989, Hodgkius fund). 
 
 2Defren (Tech. Quart., 9 (1896), No. 2-3, p. 238; E. S. E., 8, p. 385) has suggested 
 that the deleterious effect of badly ventilated rooms may be due to the presence of 
 nitrites, which he has found In considerable quantities in the air of such rooms. 
 
59 
 
 The balance of income and outgo of nitrogen and carbon and the gain 
 or loss of body protein and fat in the four experiments are briefly sum- 
 marized as follows : 
 
 Tablk 32. — Balance of income and outgo of nitrogen and carbon and gain or Ions of body 
 protein and fat in the four riS2)iration experiments. 
 
 a. 
 
 
 
 
 Nitrogen. 
 
 Carbon. 
 
 Pro- 
 tein. 
 
 Fat. 
 
 §1 
 
 
 
 <u 
 
 
 
 
 bi 
 
 
 
 
 >i 
 
 ^ 
 
 ^^ 
 
 t4 
 
 Subject. 
 
 Occupa- 
 tion. 
 
 o a 
 
 
 
 
 o 
 — ■ 1 
 
 
 
 
 3 . 
 
 o 
 
 o 
 
 O 
 
 1" 
 
 
 ja 
 
 •d 
 
 6 
 a 
 
 a> 
 
 + J, 
 
 _■ 
 
 6 
 a 
 
 i 
 
 f- a 
 »5 
 
 +x 
 
 + 1 
 
 + J, 
 
 1^ 
 
 
 
 
 1 
 
 
 1 
 
 a 
 
 M 
 
 .9 = 
 o 
 
 S 
 
 a 
 t-1 
 
 
 i 
 
 a 
 
 M 
 
 
 .s = 
 o 
 
 .9 = 
 
 a'~' 
 
 .si 
 
 a" 
 O 
 
 
 
 
 Days. 
 
 Gm«. 
 
 Oms. 
 
 Oi. 
 
 Got*. 
 
 Gw*. 
 
 (hnx. 
 
 Gmg. 
 
 6ms. 
 
 Gins. 
 
 Otns. 
 
 Oms. 
 
 1 
 
 Janitor 
 (E.O.). 
 
 Rest .... 
 
 2 
 
 45.4 
 
 39.2 
 
 1.8 
 
 + 4.4 
 
 578.6 
 
 22.7 
 
 18.0 
 
 428.2 
 
 -1-109.7 
 
 +27.5 
 
 +124. 3 
 
 2 
 
 ....do 
 
 ....do... 
 
 2 
 
 3«.4 
 
 30.1 
 
 3. 2 — 0. 9 
 
 521.2' 28.6 
 
 19. S 
 
 435. 1 
 
 + 37.7 
 
 — 5.7 
 
 + .'>3.2 
 
 3 
 
 Cliemist 
 
 Light 
 
 5 
 
 70.5 
 
 68.7 
 
 4. 5 + 3. 3 
 
 1,171.5 54.6 
 
 34. 51, 099. 6 
 
 — 17.2 
 
 +20.6 
 
 — 36.7 
 
 
 (O.F.T.). 
 
 mental 
 work. 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 Rest.... 
 
 H 
 
 2G.3 
 
 23.2 
 
 2.3+ 0.8 
 
 396.7 
 
 13.5 
 
 17.1 
 
 376.2 
 
 — 10.1 
 
 -t 5.0 
 
 — 16.6 
 
 
 
 il e ntal 
 
 3 
 
 48.6 
 
 39.4 
 
 4.2+ 5.0 
 
 732. 3 
 
 26.3 
 
 31.5 
 
 690.6 
 
 — 22.1 
 
 + 31.3 
 
 - 50.5 
 
 
 
 work. 
 
 
 
 
 
 
 
 
 
 
 
 
 4 
 
 Physicist 
 (A'W.S.). 
 
 Rest .... 
 
 3 
 
 48.6 
 
 37.4 
 
 4.21+ 7.0 
 
 732.3 
 
 32.2 
 
 31.5 
 
 713.2 
 
 — 44.6 
 
 +43. 7 
 
 — 88.6 
 
 Mil sca- 
 lar w'k. 
 
 3 
 
 48.6 
 
 42.4 
 
 4.2 
 
 + 2.0 
 
 732.3 
 
 30.1 
 
 31.51,114.6 
 
 -443.9 
 
 + 12.5 
 
 -588. 9 
 
 
 
 Rest .... 
 
 11 
 
 22.3 
 
 21.5 
 
 1.9 
 
 - 1.1 
 
 335. 6 
 
 17.2 
 
 14.4 336.6 
 
 — 32.6 
 
 -6.9 
 
 — 37.8 
 
 
 
 Whole 
 
 12 
 
 194.4 
 
 163.9 
 
 16.8 
 
 -t-13. 7 2, 929. 2119. 3|126. 0|3, 237. 2 
 
 -555. 3 
 
 +85.6 
 
 -782.4 
 
 
 
 exp't. 
 
 
 
 
 
 
 1 1 1 
 
 
 
 
 As explained previously, the total income is represented by the food 
 actually eaten (with drink and tlie oxj^gen of inhaled air), and the net 
 income by the total income minus the outgo in the feces, taking into 
 account also the incompletely oxidized material excreted in the urine. 
 The net income represents that part of* the food which is available for 
 the body. If the amount available is Just sufficient for the needs of 
 the organism it will all be burned in the body to yield energy. If it is 
 insufficient some of the body tissue will be burned also, and if it is more 
 than sufficient some material may be stored. The nitrogen in the urine is 
 assumed to represent the nitrogenous material which has been (incom- 
 pletely) burned in the body. In the present experiments it is assumed 
 that the carbon in the urine is from the same source. The carbon of 
 the respiratory products is taken as representing the carbon which has 
 been comidetely burned. 
 
 In Table 33 are shown the nitrogen, carbon, and energy in the daily 
 n(!t income and the material actually burned in the body in the four 
 experiments. 
 
60 
 
 Table 33. — Daily net income and material actually im-ned in the dody in the four 
 
 experiments. 
 
 Ex- 
 peri- 
 ment 
 num- 
 ber. 
 
 Subject. 
 
 Occupation . 
 
 Dura- 
 tion 
 
 of ex- 
 peri 
 
 ment. 
 
 Digested food. 
 
 Material burned in the 
 body. 
 
 Nitro- 
 gen. 
 
 Carbon. 
 
 Pnel 
 value. 
 
 Nitro- 
 gen, a 
 
 Carbon . 
 6 
 
 Fuel 
 value. 
 
 1 
 
 Janitor (E. 0.).-.. 
 do 
 
 Kest 
 
 Days. 
 2 
 2 
 5 
 
 If 
 .3 
 3 
 3 
 
 Grams. 
 21.8 
 17.6 
 14.4 
 
 14.8 
 14.8 
 14.8 
 14.8 
 14.8 
 14.8 
 
 Grams. 
 280. 3 
 250.7 
 227. 4 
 
 233.6 
 233. 
 233.6 
 233.6 
 233. C 
 233.6 
 
 Calories. 
 2, 970 
 2,650 
 2,460 
 
 2,525 
 2,520 
 2,495 
 2,505 
 2, 540 
 2,510 
 
 Gram,s. 
 19.6 
 18.0 
 13.7 
 
 14.3 
 13.1 
 12.5 
 14.1 
 15.2 
 13.6 
 
 Grams. 
 225.5 
 231.8 
 230.9 
 
 238.4 
 241.0 
 248.4 
 381.6 
 260.2 
 279.7 
 
 Calories. 
 ' 310 
 
 2 
 
 . ...do 
 
 2,420 
 2,505 
 
 2 585 
 
 3 
 
 Chemist (O.F.T.). 
 
 Physicist (A. W. 
 S.). 
 
 Light mental 
 work. 
 
 fRest . 
 
 4 
 
 Mental work . . 
 Rest 
 
 2, 620 
 2 695 
 
 
 Muscular work 
 
 4,325 
 2,875 
 3,085 
 
 
 
 
 
 
 
 
 a Nitrogen of urine, i. e., of incompletely oxidized nitrogenous material of food and body, 
 b Carbon of respiratory products plus that of urine. 
 
 Ill the first experiment the amount of protein was rather large. The 
 subject, a laboratory janitor, was accustomed to somewhat active mus- 
 cular work and had a very hearty appetite. The diet was of his own 
 selection and proved more than sufficient for the needs of his organism 
 during the experiment when he was comparatively inactive. His 
 organism stored both protein and fat. 
 
 In the next experiment, which was made with the same person, the 
 diet was the same in kind, but less in quantity. The ration proved 
 insufficient to maintain the nitrogen equilibrium, although some fat 
 was stored. In this case, however, the quantities of protein lost and 
 of fat gained were quite small, so that the organism was very nearly in 
 equilibrium, especially as regards nitrogen. 
 
 In the third experiment the diet was considerably smaller in protein 
 and energy than in the two preceding. The subject, a chemist, was 
 accustomed to rather less muscular labor than the subject of the first 
 and second experiments. He was also rather lighter in weight. The 
 diet which he chose was smaller in both nutrients and energy. The fig- 
 ures indicate a slight gain of protein and loss of fat during the exj)eri- 
 ment, but on the whole the organism Avas very nearly in equilibrium in 
 respect to both nitrogen and carbon. The fuel value of the material 
 actually consumed in the body was larger than in either of the two 
 preceding experiments, though somewhat smaller than that in the fourth 
 experiment under similar conditions. 
 
 In the fourth experiment the subject was a physicist. He was taller 
 than the subject of the third and heavier than either of the subjects 
 in the preceding experiments. The diet was of his own selection, as 
 in the previous cases. The amount of nitrogen was less than in the 
 first two experiments, though slightly more than in the third. The 
 potential energy of the digested food was a little larger than in that 
 o± the third experiment. ^Nevertheless, the figures indicate a slight 
 
6l~ 
 
 gain rather tliaii loss of protein during all of the periods of the e.xperi- 
 meiit wheu there Avas uo especially great luuscular activity, though 
 there was constant loss of fat from the organism. In the period of 
 muscular activity the loss of fat was very much larger, the loss of 
 carbon being 148 grams per day. 
 
 In discussing the gain or loss of protein the nitrogen lag is an imjior- 
 tant factor. It has been stated above that in experiment No. -4 au 
 allowance of six hours was made for the lag of the urine. That this 
 time was iusufticient was also pointed out, and thirty hours Avas sug- 
 gested as probably more nearly representing the period of lag. Table 
 34 gives the nitrogen and carbon in the net income and outgo for the 
 three important periods of this experiment, with the calculated nitro- 
 gen and carbon actually burned in the body aud energy liberated, 
 allowing for both six hours' lag aud thirtj^ hours' lag. 
 
 Tahle 34. 
 
 -Daily net invoine and material actually hurned in the body, allowing for 6 
 hours' and 30 hours' lag of urine. 
 
 
 o 
 e 
 
 o 
 
 t 
 n 
 o 
 
 Nitrogen. 
 
 Protein 
 gain 
 ( + )or 
 
 loss 
 
 Carbon. 
 
 Fat 
 loss. 
 
 
 
 In di- 
 gested 
 food. 
 
 In ma- 
 terial 
 burned 
 in the 
 body. 
 
 Gain 
 
 (+) or 
 loss 
 (-)• 
 
 Indi 
 gestcd 
 food. 
 
 In ma- 
 terial 
 
 burned 
 in the 
 body. 
 
 Loss. 
 
 Fuel- 
 value 
 loss. 
 
 Allowing 6 hours' 
 lag: 
 
 Menial work 
 
 Ke.st 
 
 Days. 
 3 
 3 
 3 
 
 3 
 3 
 3 
 
 Gramt. 
 14.8 
 14.8 
 14.8 
 
 14.8 
 14.8 
 14.8 
 
 Grains. 
 13.1 
 12.5 
 14.1 
 
 12.7 
 12.4 
 15.6 
 
 Grams. 
 +1.7 
 + 2.3 
 +0.7 
 
 +2.1 
 +2.4 
 —0.8 
 
 Grams. 
 +10.4 
 +14.6 
 + 14.2 
 
 + 13.0 
 + 15.0 
 — 5.0 
 
 Grams. 
 233.6 
 233. 6 
 233.6 
 
 233. 6 
 233. 6 
 233.6 
 
 Grams. 
 241.0 
 248.4 
 381.5 
 
 243.3 
 247.0 
 382.4 
 
 Grams. 
 
 — 7.4 
 
 — 14.8 
 -147. 9 
 
 — 9.7 
 
 — 13.4 
 -148.8 
 
 Grams. 
 
 — 16.8 
 
 — 29.5 
 —196. 3 
 
 — 21.7 
 
 — 27.8 
 —191. 
 
 Calories. 
 
 — 100 
 
 M 11 SCI liar work . 
 A UowingSO hours' 
 lag: 
 
 Mental work 
 
 Kest 
 
 —1, 820 
 
 - 135 
 180 
 
 Muscular work . 
 
 —1, 825 
 
 When the nitrogen lag is assumed to be six hours there is a small 
 gain of protein <luring the period of muscular work; but when it is 
 assumed to be thirty hours there is a small loss. When a thirty-hour 
 nitrogen lag is assumed the gains in protein during the periods of rest 
 and mental labor are somewhat larger than when a six-hour lag is 
 assumed. 
 
 It will be noticed that there are marked differences in the ways the 
 sul)iects in the four exi)eriment8 utilized the food material at tlieir 
 ilisposal. Tlie dineiences in age, weight, occui>ation, and diet have 
 been refcired to. It will, however, be of interest to add that some 
 studies had been i)reviously made which throw a little more light upon 
 the <lietary habits of two of them. 
 
 Two dietary studies were made in the family of the laboratory janitor, 
 one in February and the other in March, 18!M.' In these tlie average 
 ])rotein in the food eaten per man per day was estimated at 120 grams, 
 
 ' 8eo Report of Htorrs (Couu.) Agricultural Experiuieut Station, 18'J4, pp. IHO :in<l liiS. 
 
62 
 
 and the total energy of tlie nutrients at 3,900 calories. The correspond- 
 ing amounts digested were estimated at approximately 116 grams of 
 protein and 3,660 calories. This was, on the whole, a liberal diet. It 
 is slightly larger than the American standard' suggested for a man at 
 moderately severe muscular work. 
 
 Two dietary studies were made by the subject of experiment No. 4 
 at his home in a country town in another State, on the occasions of 
 vacation visits, one in the winter and the other in summer.^ There was 
 but little difference between the results of the two. It seems fair to 
 assume that they may represent the dietary habits which the subject 
 had naturally acquired. The averages per man per day were approxi- 
 mately 79 grams of protein and 3,125 calories of energy. These quan- 
 tities are estimated to correspond to about 71 grams of protein and 
 2,955 calories of energy in the food actually digested. 
 
 It will be observed that, according to the above estimates, the labo- 
 ratory janitor, who was accustomed to moderately active muscular 
 work ten hours per day, and who was what would be called a "hearty 
 eater," actually burned during the first experiment 122 grams of the 
 136 grams of digestible protein in his food and at the same time stored 
 the remaining 14 grams, according to the calculations of these experi- 
 ments. Of the 2,970 calories in the food digested he burned material 
 . corresponding to 2,310 calories. The digested nutrients of the food 
 furnished an excess of carbohydrates and fats as well as protein, so 
 that his organism stored fat and protein corresponding to 660 calories 
 of energy. In the second experiment his diet was reduced so as to 
 supply only 110 grams of digestible protein and 2,650 calories of energy. 
 In this case his organism was estimated to burn 113 grams of protein, 
 a trifle more than the food supplied, and 2,420 calories of energy. The 
 organism gained considerable fat, enough to make a gain of material 
 corresponding to 230 calories of energy. 
 
 The subjects of experiments ISTos. 3 and 4, who were accustomed to 
 only light muscular activity, chose for their diet materials computed 
 to supply 90 and 93 grams of digestible protein, respectively, and other 
 digestible nutrients sufficient to furnish about 2,500 calories of energy 
 per day. In the respiration apparatus when at rest or engaged in 
 either light or severe mental work they burned in the body from 78 to 
 86 grams of protein and from about 2,500 to 2,700 calories of energy. 
 It was evident that this consumption must have been reasonably eco- 
 nomical, since the food in experiment No. 3 supplied only a trifle more 
 protein and a trifle less energy than was utilized; while in experiment 
 No. 4, when the subject was at rest or engaged in mental work there 
 was with a slight apparent gain of protein a decided loss of fat. Al- 
 though the subject of experiment No. 4 was a man of larger frame and 
 greater weight than the subject of experiment No. 3, his organism 
 
 lU. S. Dept. Agr., Office of Experiment Stations Bui. 21, p. 213. 
 '^See Eeports of Storrs (Conn.) Experiment Station, 1895, p. 137, and 1896, p. 144. 
 
63 
 
 Imrued less protein : but this seems to accord with the results of dietary 
 studies meutioued above, which im[)lies that he was in the habit of con- 
 suming small quantities of protein. While his organism burned smaller 
 quantities of protein, it burned more fat and utilized more energj' than 
 was the case with the subject of experiment Jfo. 3. When the same 
 person engaged in severe muscular work the amount of protein burned 
 rose from 78 to 98 grams per day. At the same time the energy utilized 
 rose from 2,695 to 4,.'525 calories. That there should be such an increase 
 in the amount of both protein burned and energy utilized with the 
 severe muscular work is not at all suri)rising. How the amount of pro- 
 tein burned during the period of muscular work would have been 
 affected if the quantity of carbohydrates and fats had been sufficient 
 to sui)ply the needed energy is a question to be answered by further 
 experiment. 
 
 OONCLrSIOJfS. 
 
 The experiments above described offer considerable material for dis- 
 cussion. Since, however, they are of a preliminary character and are 
 to be followed by others in which the results of the experience here 
 obtained will be used, it is deemed best to reserve the discussion until 
 more of the anticipated work shall have been accomplished. Mean- 
 while the following statements are i)erhai)S in place: 
 
 (1; The experience here obtained emjjhasizes the desirability of 
 longer exi>erimeutal j'criods than have been customary in experiments 
 of this class. Although a considerable number of resjjiration experi- 
 ments have been made with animals and man, the periods have rarely 
 exceeded twentj'-four hours. The hgures in the tables above are suffi- 
 cient to show that the results obtained in periods so short are less con- 
 clusive than is to be desired. 
 
 (2) Much care needs to be bestowed upon the analyses of the mate- 
 rials of income and outgo. In tlie majority of experiments thus far 
 rejiorted the composition of food and solid and liquid excretory prod- 
 ucts has been in large part assumed, ratljer than estimated from direct 
 analyses of specimens of the materials belonging to the experiments. 
 In like manner there is need of the greatest possible care and accuracy 
 in the determination of the gaseous excretory products. Xor can any 
 of the organic matters given oft' in ])ersi)iration and exhalation be left 
 out of acc^>unt if the fullest accuracy is to be attained. 
 
 (3) It is to be hoped that future exjierience may lead to sn(;h 
 impiovements as shall insure the accurate measurement of all the 
 chemical elements involved in the income and outgo. It is evident that 
 there are no insurmountable obstacles in the way of reasonably accu- 
 rate estimation of the incom(; and outgo of nitrogen and carbon. As 
 regards the hydrogen, the difficulties of determination ha\e thus far 
 been more serious, but they do not appear to be by any means insur- 
 mountable. The <juantitie8 of sulphur and i)hosphoru.s are so small 
 that extreme accuracy is needed for their estimation in order to insure 
 
64 
 
 satisfactory comparison of income and outgo. The experience gained 
 in this laboratory since the exj)eriments here described were made indi- 
 cates that by refinement of methods reasonably reliable results may be 
 obtained. 
 
 (4) The prospects for obtaining a satisfactory balance of income and 
 outgo of energy are, on the whole, decidedly encouraging. The deter- 
 minations of heats of combustion by the bomb calorimeter are emi- 
 nently satisfactory, aud there seems to be good ground to hope that 
 ultimately the measurements of heat given off from the body may also 
 prove sufficiently accurate for such purposes. Satisfactory results have 
 already been reported by other experimenters with small animals and 
 with men during experiments of short duration. Experience in this 
 laboratory since the above experiments were made have yielded results 
 agreeing very closely indeed with the theoretical figures. 
 
 (5) The results of these experiments and of similar investigations 
 elsewhere bring out very clearly the difference in the amounts of nutri- 
 ents and energy required by the organisms of different persons under 
 different conditions, and confirm the results of previous inquiry in 
 showing that muscular labor is performed at the expense of the fats, 
 sugars, and starches. They also make it clear that the body may draw 
 upon protein for this j)urpose, although it has not yet been determined 
 just what are the conditions under which this is done. A large amount 
 of work will be needed to secure the experimental data necessary for 
 accurate generalizations. The importance of the subject is such as to 
 call for the most extensive and i^ainstaking research. 
 

 Date Due 
 
 ■i 
 
 
 
 
 
 
 i ii^L t fe l|k* 
 
 "D,;^a^. Ml 
 
 i-i%im' 
 
 
 ^Sile ® d 
 
 - ■' ■■.:/. 
 
 - 
 
 
 
 ., ;.. '-v^i^ 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 ^ 
 
 
 
 
COLUMBIA UNIVERSITY LIBRARlPg 
 
 QP171 
 
 Atwater 
 
 At93 
 
 ^^, Metabolism of Jiitrogea,^ 
 
 and carbo|n in the human organism 
 
 .u^ 1 711941 P.