80 



SCIENCE 



[N. S. Vol. XLII. No. 1072 



have simultaneously recorded the total dis- 

 tance walked, the number of steps, the in- 

 clination of the treadmill and the total 

 height of the body movement. By attach- 

 ing a cord to the shoulders and connecting 

 it with a pointer, a record of the up-and- 

 down motion of the body with each step is 

 made, and by a multiplying device the total 

 sum of the upward motions of the body are 

 also recorded, thus giving the total height 

 to which the body is raised during the 

 period of walking, for in walking on a 

 level plain, an individual raises his body 

 from 1 to 1^ inches each step. 



Connected with the ventilating air cur- 

 rent of the respiration apparatus is a deli- 

 cately-counterpoised beU or gas-holder, 

 which rises and falls with each respiration. 

 By means of a pointer attached to the 

 counterpoise of this bell, a graphic record 

 of the type of respiration is obtained. A 

 multiplying device attached permits the 

 measurement of the total amount of air 

 actually passing through the lungs inde- 

 pendent of the ventilation of the respira- 

 tion apparatus itself. This graphic record 

 of the ventilation of the lungs likewise 

 records the respiration rate. Finally, by 

 means of electrodes attached to the chest, 

 the pulse rate of a walking man is photo- 

 graphically recorded with a string galva- 

 nometer or an oscillograph. 



The intimate relationship between pulse- 

 rate and the total energy output has been 

 the subject of special study, and the pulse- 

 rate, the respiration-rate, and particularly 

 the body temperature have received especial 

 attention in our several lines of investi- 

 gation. The distribution of a number of 

 delicate thermometers in different parts 

 and cavities of the body has shown that 

 when the temperature deep in the body 

 trunk undergoes its regular daily rhythm, 

 these fluctuations in temperature are ac- 

 companied by similar fluctuations in all the 



other thermometers, and that while the 

 absolute temperatures in different parts of 

 the body are unlike, the fluctuations in 

 temperature are essentially the same 

 throughout the whole body. 



It has long been known that when food 

 is eaten the body activities are considerably 

 increased. This is particularly the case 

 when the food consists of protein material. 

 The exact cause of this increase has long 

 been the subject of much discussion. On 

 the one hand it was believed that this was 

 due to the work of digestion in the digestive 

 tract ; on the other hand, that it was due to 

 an excess heat production caused by the 

 splitting off and combustion of portions of 

 the protein molecule. A long series of in- 

 vestigations in the Nutrition Laboratory has 

 shown that when peristaltic stimuli, such 

 as saline purgatives, were used and careful 

 control tests made, the movements of the 

 digestive tract did not measurably increase 

 the metabolism. When dogs who had defi- 

 cient digestive capacity were fed large 

 amounts of meat, in spite of the excess of 

 undigested residue, the metabolism was not 

 augmented. Evidence has been accumu- 

 lated which shows that the acid products of 

 cleavage in the processes of digestion are 

 probably the chief factors causing this in- 

 crease in metabolism, which was explained 

 by the direct stimulus of the cells to a 

 greater activity. 



One of the most interesting researches 

 developing from the comparison of meth- 

 ods for studying the respiratory exchange 

 has been the importance of knowing phj'si- 

 ologically the exact composition of outdoor 

 air. Every person is continually taking air 

 into the lungs. Many technical methods 

 for determining the amount of oxygen thus 

 consumed involve some assumption as to the 

 exact composition of the normal outdoor air 

 inhaled. An investigation lasting over 

 three years, in which daily analyses of 



