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Introduction 1

Calorimeter laboratory 3 General plan of calorimeter laboratory 3 Heating and ventilating 7

The calorimeter 10 Fundamental principles of the apparatus 10 The calorimeter chamber 11 General construction 14 Prevention of radiation 17 The thermo-electric elements 19 Interior of the calorimeter 20 Heat-absorbing circuit 22 Thermometers 26 Mercurial thermometers 26 Electric-resistance thermometers 28 Air-thermometers 28 Wall thermometers 29 Electrical rectal thermometer 29 Electric-resistance thermometers for the water-current 29 Observer's table 31 Connections to thermal-junction systems 33 Rheostat for heating 34 Wheatstone bridges 34 Galvanometer 35 Resistance for heating coils 35 Temperature recorder 36 Fundamental principle of the apparatus 38 The galvanometer 39 The creeper 40 The clock 42 Installation of the apparatus 42 Temperature control of the ingoing air 43 The heat of vaporization of water 44 The bed calorimeter 45 Measurements of body-temperature 48 Control experiments with the calorimeter 50 Determination of the hydrothermal equivalent of the calorimeter 52

General description of the respiration apparatus 54 Testing the chamber for tightness 54 Ventilation of the chamber 54 Openings in the chamber 55 Ventilating air-current 57 Blower 57 Absorbers for water-vapor 58 Potash-lime cans 60 Balance for weighing absorbers 61 Purification of the air-current with sodium bicarbonate 63 Valves 63 Couplings 64 Absorber table 65 Oxygen supply 67 Automatic control of oxygen supply 69 Tension equalizer 71 Barometer 72 Analysis of residual air 73 Gas-meter 75 Calculation of results 76 Analysis of oxygen 76 Advantage of a constant-temperature room and temperature control 77 Variations in the apparent volume of air 77 Changes in volume due to the absorption of water and carbon dioxide 78 Respiratory loss 78 Calculation of the volume of air residual in the chamber 79 Residual analyses 80 Calculation from residual analyses 80 Influence of fluctuations in temperature and pressure on the apparent volume of air in the system 83 Influence of fluctuations in the amounts of carbon dioxide and water-vapor upon residual oxygen 83 Control of residual analyses 84 Nitrogen admitted with the oxygen 84 Rejection of air 85 Interchange of air in the food aperture 85 Use of the residual blank in the calculations 86 Abbreviated method of computation of oxygen admitted to the chamber for use during short experiments 88 Criticism of the method of calculating the volume of oxygen 89 Calculation of total output of carbon dioxide and water-vapor and oxygen absorption 91 Control experiments with burning alcohol 91 Balance for weighing subject 93 Pulse rate and respiration rate 95 Routine of an experiment with man 96 Preparation of subject 96 Sealing in the cover 97 Routine at observer's table 97 Manipulation of the water-meter 98 Absorber table 99 Supplemental apparatus 100

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Fig. 1. General plan of respiration calorimeter laboratory 4

RESPIRATION CALORIMETERS FOR STUDYING THE RESPIRATORY EXCHANGE AND ENERGY TRANSFORMATIONS IN MAN.

INTRODUCTION.

The establishment in Boston of an inquiry into the nutrition of man with the construction of a special laboratory for that purpose is a direct outcome of a series of investigations originally undertaken in the chemical laboratory of Wesleyan University, in Middletown, Connecticut, by the late Prof. W. O. Atwater. Appreciating the remarkable results of Pettenkofer and Voit and their associates, as early as 1892 he made plans for the construction of a respiration apparatus accompanied by calorimetric features. The apparatus was designed on the general ventilation plan of the above investigators, but in the first description of this apparatus it is seen that the method used for the determination of carbon dioxide and water-vapor was quite other than that used by Voit. Each succeeding year of active experimenting brought about new developments until, in 1902, the apparatus was essentially modified by changing it from the open-circuit type to the closed-circuit type of Regnault and Reiset. This apparatus, thus modified, has been completely described in a former publication. The calorimetric features likewise underwent gradual changes and, as greater accuracy was desired, it was found impracticable to conduct calorimetric investigations to the best advantage in the basement of a chemical laboratory. With four sciences crowded into one building it was practically impossible to devote more space to these researches. Furthermore, the investigations had proceeded to such an extent that it seemed desirable to construct a special laboratory for the purpose of carrying out the calorimetric and allied investigations on the nutrition of man.

In designing this laboratory it was planned to overcome the difficulties experienced in Middletown with regard to control of the room-temperature and humidity, and furthermore, while the researches had heretofore been carried on simultaneously with academic duties, it appeared absolutely necessary to adjust the research so that the uninterrupted time of the experimenters could be given to work of this kind. Since these experiments frequently continued from one to ten days, their satisfactory conduct was not compatible with strenuous academic duties.

As data regarding animal physiology began to be accumulated, it was soon evident that there were great possibilities in studying abnormal metabolism, and hence the limited amount of pathological material available in Middletown necessitated the construction of the laboratory in some large center.

A very careful consideration was given to possible sites in a number of cities, with the result that the laboratory was constructed on a plot of ground in Boston in the vicinity of large hospitals and medical schools. Advantage was taken, also, of the opportunity to secure connections with a central power-plant for obtaining heat, light, electricity, and refrigeration, thus doing away with the necessity for private installation of boilers and electrical and refrigerating machinery. The library advantages in a large city were also of importance and within a few minutes' walk of the present location are found most of the large libraries of Boston, particularly the medical libraries and the libraries of the medical schools.

The building, a general description of which appeared in the Year Book of the Carnegie Institution of Washington for 1908, is of plain brick construction, trimmed with Bedford limestone. It consists of three stories and basement and practically all the space can be used for scientific work. Details of construction may be had by reference to the original description of the building. It is necessary here only to state that the special feature of the new building with which this report is concerned is the calorimeter laboratory, which occupies nearly half of the first floor on the northern end of the building.

FOOTNOTES:

Pettenkofer and Voit: Ann. der Chem. u. Pharm. , Supp. Bd. 2, p. 17.

Atwater, Woods, and Benedict: Report of preliminary investigations on the metabolism of nitrogen and carbon in the human organism with a respiration calorimeter of special construction, U. S. Dept. of Agr., Office of Experiment Stations Bulletin 44.

W. O. Atwater and F. G. Benedict: A respiration calorimeter with appliances for the direct determination of oxygen. Carnegie Institution of Washington Publication No. 42.

CALORIMETER LABORATORY.

The laboratory room is entered from the main hall by a double door. The room is 14.2 meters long by 10.1 meters wide, and is lighted on three sides by 7 windows. Since the room faces the north, the temperature conditions are much more satisfactory than could be obtained with any other exposure. In constructing the building the use of columns in this room was avoided, as they would interfere seriously with the construction of the calorimeters and accessory apparatus. Pending the completion of the five calorimeters designed for this room a temporary wooden floor was laid, thus furnishing the greatest freedom in placing piping and electric wiring beneath the floor. As fast as the calorimeters are completed, permanent flooring with suitably covered trenches for pipes is to be laid. The room is amply lighted during the day, the windows being very high, with glass transoms above. At night a large mercury-vapor lamp in the center of the room, supplemented by a number of well-placed incandescent electric lights, gives ample illumination.

GENERAL PLAN OF CALORIMETER LABORATORY.

The general plan of the laboratory and the distribution of the calorimeters and accessory apparatus are shown in fig. 1. The double doors lead from the main hall into the room. In general, it is planned to conduct all the chemical and physical observations as near the center of the laboratory as possible, hence space has been reserved for apparatus through the center of the room from south to north. The calorimeters are on either side. In this way there is the greatest economy of space and the most advantageous arrangement of apparatus.

At present two calorimeters are completed, one under construction, and two others are planned. The proposed calorimeters are to be placed in the spaces inclosed by dotted lines. Of the calorimeters that are completed, the so-called chair calorimeter, which was the first built, is in the middle of the west side of the room, and immediately to the north of it is the bed calorimeter, already tested and in actual use. On the east side of the room it is intended to place large calorimeters, one for continuous experiments extending over several days and the other large enough to take in several individuals at once and to have installed apparatus and working machinery requiring larger space than that furnished by any of the other calorimeters. Near the chair calorimeter a special calorimeter with treadmill is shortly to be built.

The heat insulation of the room is shown by the double windows and the heavy construction of the doors other than the double doors. On entering the room, the two calorimeters are on the left, and, as arranged at present, both calorimeters are controlled from the one platform, on which, is placed the observer's table, with electrical connections and the Wheatstone bridges for temperature measurements; above and behind the observer's table are the galvanometer and its hood. At the left of the observer's platform is a platform scale supporting the water-meter, with plug valve and handle conveniently placed for emptying the meter. The absorption system is placed on a special table conveniently situated with regard to the balance for weighing the absorbers. The large balance used for weighing the oxygen cylinders is directly across the center aisle and the analytical balance for weighing the U-tubes for residual analysis is near by.

Another view of the laboratory, taken near the door leading to the refrigeration room, is shown in fig. 3. At the right is seen the balance used for weighing absorbers, and back of it, imperfectly shown, is the case surrounding the balance for weighing oxygen cylinders. On the wall, in the rear, is the recording apparatus for electric resistance thermometers in the water-circuit, a detail of which is shown in fig. 23. In the foreground in the center is seen the observer's table; at the right of this is shown the table for the absorption system, and at the left the chair calorimeter with the balance for weighing subjects above it. The mercury-vapor light, which is used to illuminate the room, is immediately above the balance for weighing absorbers.

The bed calorimeter and the absorbing-system table are better shown in fig. 4, a general view of the laboratory taken near the temperature recorder. In the immediate foreground is the table for the absorption system, and back of it are the observer's table and chair calorimeter. At the right, the bed calorimeter with the front removed and the rubber hose connections as carried from the absorber table to the bed calorimeter are shown. At the extreme left is the balance for weighing the absorbers. Above the chair calorimeter can be seen the balance for weighing the subject, and at its right the galvanometer suspended from the ceiling.

The west side of the laboratory at the moment of writing contains the larger proportion of the apparatus. On the east side there exist only the balance for weighing oxygen cylinders and an unfinished large calorimeter, which will be used for experiments of long duration. A view taken near the front end of the bed calorimeter is shown in fig. 5. At the right, the structural skeleton of the large calorimeter is clearly shown. Some of the copper sections to be used in constructing the lining of the calorimeter can be seen against the wall in the rear.

At the left the balance for weighing the oxygen cylinders is shown with its counterpoise. A reserve oxygen cylinder is standing immediately in front of it. A large calorimeter modeled somewhat after the plan of Sond?n and Tigerstedt's apparatus in Stockholm and Helsingfors is planned to be built immediately back of the balance for weighing oxygen cylinders.

HEATING AND VENTILATING.

Of special interest in connection with this calorimeter laboratory are the plans for maintaining constant temperature and humidity . The room is heated by five steam radiators placed about the outer wall, which are controlled by two pendant thermostats. A certain amount of indirect ventilation is provided, as indicated by the arrows on the inner wall. The room is cooled and the humidity regulated by a system of refrigeration installed in an adjoining room. This apparatus is of particular interest and will be described in detail.

In the small room shown at the south side of the laboratory is placed a powerful electric fan which draws the air from above the floor of the calorimeter laboratory, draws it over brine coils, and sends it out into a large duct suspended on the ceiling of the laboratory. This duct has a number of openings, each of which can be controlled by a valve, and an unlimited supply of cold air can be directed to any portion of the calorimeter room at will. To provide for more continuous operation and for more exact temperature control, a thermostat has been placed in the duct and is so constructed as to operate some reheater coils beneath the brine-coils in the refrigerating room. This thermostat is set at 60? F., and when the temperature of the air in the duct falls below this point, the reheater system is automatically opened or closed. The thermostat can be set at any point desired. Up to the present time it has been unnecessary to utilize this special appliance, as the control by hand regulation has been most satisfactory.

Two vertical sections through the refrigerating coils are shown in fig. 6. Section A-B shows the entrance near the floor of the calorimeter room. The air is drawn down over the coils, passes through the blower, and is forced back again to the top of the calorimeter room into the large duct. If outdoor air is desired, a special duct can be connected with the system so as to furnish outdoor air to the chamber. This has not as yet been used. Section C-D shows the fan and gives a section through the reheater. The brine coils, 400 meters long, are in triplicate. If one set becomes covered with moisture and is somewhat inefficient, this can be shut off and the other two used. When the frozen moisture melts and drops off, the single coil can be used again. It has been found that the system so installed is most readily controlled.

The degree of refrigeration is varied in two ways: the area of brine coils can be increased or decreased by using one, two, or all three of the coils; or the amount of air passing over the cooling pipes may be varied by changing the speed of the blower. In practice substantially all of the regulation is effected by varying the position of the controlling lever on the regulating rheostat. The apparatus functionates perfectly and the calorimeter room can be held at 20? C. day in and day out, whether the temperature outdoors is 40? below or 100? above 0? F.

It can be seen, also, that this system provides a very satisfactory regulation of the humidity, for as the air passes over the brine coils the moisture is in large part frozen out. As yet, no hygrometric study has been made of the air conditions over a long period, but the apparatus is sufficiently efficient to insure thorough electrical insulation and absence of leakage in the intricate electrical connections on the calorimeters.

The calorimeters employ the thermo-electric element with its low potential and a D'Arsonval galvanometer of high sensibility, and in close proximity it is necessary to use the 110-volt current for heating, consequently the highest degree of insulation is necessary to prevent disturbing leakage of current.

The respiration calorimeter laboratory is so large, the number of assistants in the room at any time is so small, seldom exceeding ten, and the humidity and temperature are so very thoroughly controlled, that as yet it has been entirely unnecessary to utilize even the relatively small amount of indirect ventilation provided in the original plans.

During the greater part of the winter it is necessary to use only one of the thermostats and the radiators connected with the other can be shut off, since each radiator can be independently closed by the valves on the steam supply and return which go through the floor to the basement. The temperature control of this room is therefore very satisfactory and economical.

It is not necessary here to go into the advantages of temperature control of the working rooms during the summer months. Every one seems to be thoroughly convinced that it is necessary to heat rooms in the winter, but our experience thus far has shown that it is no less important to cool the laboratory and control the temperature and moisture during the summer months, as by this means both the efficiency and endurance of the assistants, to say nothing of the accuracy of the scientific measurements, are very greatly increased. Arduous scientific observations that would be wholly impossible in a room without temperature control can be carried on in this room during the warmest weather.

FOOTNOTES:

As this report goes to press, this calorimeter is well on the way to completion.

THE CALORIMETER.

In describing this apparatus, for the sake of clearness, the calorimetric features will be considered before the appliances for the determination of the respiratory products.

FUNDAMENTAL PRINCIPLES OF THE APPARATUS.

The measurements of heat eliminated by man, as made by this apparatus, are based upon the fact that the subject is inclosed in a heat-proof chamber through which a current of cold water is constantly passing. The amount of water, the flow of which, for the sake of accuracy, is kept at a constant rate, is carefully weighed. The temperatures of the water entering and leaving the chamber are accurately recorded at frequent intervals. The walls of the chamber are held adiabatic, thus preventing a gain or loss of heat by arbitrarily heating or cooling the outer metal walls, and the withdrawal of heat by the water-current is so controlled, by varying the temperature of the ingoing water, that the heat brought away from the calorimeter is exactly equal in amount to the heat eliminated by radiation and conduction by the subject, thus maintaining a constant temperature inside of the chamber. The latent heat of the water vaporized is determined by measuring directly the water vapor in the ventilating air-current.

In the construction of the new calorimeters a further and fundamental change in construction has been made in that all the thermal junctions, heating wires, and cooling pipes have been attached directly to the zinc wall of the calorimeter, leaving the outer insulating panels free from incumbrances, so that they can be removed readily and practically all parts inspected whenever desired without necessitating complete dismantling of the apparatus. This arrangement is possible except in those instances where connections pass clear through from the interior of the chamber to the outside, namely, the food-aperture, air-pipes, water-pipes, electrical connections, and tubes for connections with pneumograph and stethoscope; but the apparatus is so arranged as to have all of these openings in one part of the calorimeter. It is possible, therefore, to remove all of the outer sections of the calorimeter with the exception of panels on the east side.

This fundamental change in construction has proven highly advantageous. It does away with the necessity of rolling the calorimeter out of its protecting insulating house and minimizes the delay and expense incidental to repairs or modifications. As the calorimeter is now constructed, it is possible to get at all parts of it from the outside, with the exception of one small fixed panel through which the above connections are passed. This panel, however, is made as narrow as possible, so that practically all changes can be made by taking out the adjacent panels.

THE CALORIMETER CHAMBER.

The respiration chamber used in Middletown, Connecticut, was designed to permit of the greatest latitude in the nature of the experiments to be made with it. As a result, it was found at the end of a number of years of experimenting that this particular size of chamber was somewhat too small for the most satisfactory experiments during muscular work and, on the other hand, somewhat too large for the best results during so-called rest experiments. In the earlier experiments, where no attempt was made to determine the consumption of oxygen, these disadvantages were not so apparent, as carbon dioxide could be determined with very great accuracy; but with the attempts to measure the oxygen it was found that the large volume of residual air inside the chamber, amounting to some 4,500 liters, made possible very considerable errors in this determination, for, obviously, the subject could draw upon the oxygen residual in the air of the chamber, nearly 1,000 liters, as well as upon the oxygen furnished from outside sources. The result was that a very careful analysis of the residual air must be made frequently in order to insure that the increase or decrease in the amount of oxygen residual in the air of the chamber was known accurately at the end of each period. Analysis of this large volume of air could be made with considerable accuracy, but in order to calculate the exact total of oxygen residual in the air it was necessary to know the total volume of air inside the chamber under standard conditions. This necessitated, therefore, a careful measurement of temperature and pressure, and while the barometric pressure could be measured with a high degree of accuracy, it was found to be very difficult to determine exactly the average temperature of so large a mass of air. The difficulties attending this measurement and experiments upon this point are discussed in detail elsewhere. Consequently, as a result of this experience, in planning the calorimeters for the Nutrition Laboratory it was decided to design them for special types of experiments. The first calorimeter to be constructed was one which would have general use in experiments during rest and, indeed, during experiments with the subject sitting quietly in the chair.

It may well be asked why the first calorimeter was not constructed of such a type as to permit the subject assuming a position on a couch or sofa, such as is used by Zuntz and his collaborators in their research on the respiratory exchange, or the position of complete muscular rest introduced by Johansson and his associates. While the body positions maintained by Zuntz and Johansson may be the best positions for experiments of short duration, it was found, as a result of a large number of experiments, that subjects could be more comfortable and quiet for periods of from 6 to 8 hours by sitting, somewhat inclined, in a comfortable arm-chair, provided with a foot-rest. With this in mind the first calorimeter was constructed so as to hold an arm-chair with a foot-rest so adjusted that the air-space between the body of the subject and the walls of the chamber could be cut down to the minimum and thus increase the accuracy of the determination of oxygen. That the volume has been very materially reduced may be seen from the fact that the total volume of the first calorimeter to be described is less than 1,400 liters, or about one-third that of the Middletown apparatus.

GENERAL CONSTRUCTION.

A horizontal cross-section of the apparatus is shown in fig. 7, and a vertical cross-section facing the front is given in fig. 8. Other details of structural steel are seen in fig. 9.

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