NUTRITION LABORATORY. 215 



its successful operation. No satisfactory substitute therefor has as yet been 

 found. By the introduction of a highly accurate psychrometer and modified 

 methods of sampling the air inside the respiration chamber, and by making 

 use of the remarkable gas-analysis apparatus devised by Dr. Klas Sonden, 

 we have been able to rearrange completely the routine for conducting ex- 

 periments with this apparatus, thereby increasing both the accuracy and the 

 facility of operation and decreasing the cost. A simple but very important 

 modification in the bed calorimeter is the suspension of the bed on knife- 

 edges and a stout spiral spring in such manner as to give exact graphic 

 records of the degree of restlessness of the subject during the experiment. 

 These records have proved invaluable in the interpretation of many of the 

 experimental results. 



TREADMILL. 



A respiration chamber especially designed for severe muscular work was 

 mentioned in a previous report, and its construction has proceeded regularly 

 though slowly since that time. While connected with the laboratory stafif a 

 few years ago, Mr. E. H, Metcalf designed a treadmill for use with man 

 which has recently been constructed, tested, and found most satisfactory. 

 This treadmill consists of a wide leather belt passing over two pulleys, the 

 belt being further supported by a large number of steel tubes with ball bear- 

 ings in each end. The apparatus has proved most efficient, runs with a mini- 

 mum amount of noise, and should prove a most valuable adjunct in studying 

 the motion of forward progression, the work of ascent and descent, and 

 similar physiological problems. 



RESPIRATION APPARATUS. 



The number of researches which can be carried out satisfactorily with the 

 small respiration apparatus devised in this laboratory has been found to be 

 so great that several additional apparatus were constructed. Important 

 modifications recently introduced permit a more extensive use of this method, 

 inasmuch as pathological cases may be studied, thus giving greater value to 

 the results obtained. By the addition of a very lightly counterpoised spir- 

 ometer, graphic records of the character, amplitude, and volume of each 

 respiration are secured, A simple device also makes possible the accurate 

 record of the total volume of air passing through the lungs. A number of 

 clinicians have been experimenting with this apparatus and pronounce it of 

 very great value. 



MODIFICATION OF THF APPARATUS FOR FXPFRIMENTS ON SEVERE 



MUSCULAR WORK. 



In connection with the research undertaken by Dr. E. P. Cathcart, of 

 Glasgow, during the past winter, it was necessary to modify somewhat the 

 respiration apparatus to permit accurate measurements of the enormous vol- 



