NUTRITION LABORATORY. 



227 



In the second part of the report is given a description of an accurate gas- 

 analysis apparatus devised by Dr. Klas Sonden, of Stockholm, together with 

 the technique of its use and the results of a series of analyses of outdoor air 

 covering nearly three years, which were made by Miss Alice Johnson in the 

 Nutrition Laboratory. The steps in the elimination of individual errors in 

 the technique and routine are carefully traced until finally the conclusion is 

 reached that uncontaminated outdoor air in Boston is of constant oxygen 

 content, irrespective of conditions of weather, humidity, temperature, barom- 

 eter, wind direction, etc. Further analyses of air taken from many points 

 on the Atlantic Ocean and from the top of Pike's Peak showed a like uni- 

 formity in composition. The average results of all the analyses made in 

 this research of outdoor air are summarized in the table presented herewith : 



*In water and carbon dioxide-free air. 



(8) A bicycle ergometer with an electric brake. Francis G. Benedict and Walter G. 

 Cady. Publication No. 167, Carnegie Institution of Washington. 1912. 



A form of stationary bicycle in which the rear wheel is replaced by a cop- 

 per disk rotating in an electro-magnetic field has been extensively used in 

 this laboratory for measurements of the mechanical work of man. Certain 

 important calibration tests, friction measurements, and particularly the pe- 

 culiar magnetic reaction produced by the copper disk rotating between the 

 poles of the magnet, are described in this publication. Two instruments 

 were used, one having been calibrated several years before. The new cali- 

 bration of this latter instrument showed essentially the same values as the 

 earlier tests. The speed usually assumed by a bicycle rider ranges from 60 

 to 90 revolutions per minute, and at these speeds the ergometer, singularly 

 enough, gives essentially the same heat per revolution. At slower and 

 higher speeds there is a marked decrease in the heat per revolution. A 

 careful study of the magnetic reactions in the disk showed the peculiarly 

 interesting demagnetizing effect of the eddy current in the disk. The re- 

 search has led to many theoretical as well as practical deductions. 



(9) Some fundamental principles in studying infant metabolism. Francis G. Benedict 

 and Fritz B. Talbot. Amer. Jour. Diseases of Children, 4, p. 129. 1912. 



With a modified form of the universal respiration apparatus used in this 

 laboratory and designed for studying the metabolism of infants, a research 

 has been carried out to determine the metabolism from the carbon-dioxide 

 production. A portion of the results are presented in this paper. Especial 

 care was taken to secure a continuous record of the pulse-rate by means of a 

 Bowles stethoscope attached to the chest of the infant, and in addition a 

 graphic record of the minor muscular activities of the sleeping child, to 

 determine their relationship with the metabolism. For the purpose of sup- 

 plementing these records, a number of observations were made in two Bos- 

 ton hospitals of the pulse-rate of babies at various times of the day. The 

 wide fluctuations in these records, even during periods of sleep, are shown 



