496 



SCIENCE. 



[N. S. Vol. V. No. 117. 



formed severe muscular exercise. During 

 eight hours of each of the 3 days he was 

 engaged in raising and lowering a heavy 

 weight which was suspended by a cord 

 passing over a pulley at the top of the 

 chamber. The work in this case was so 

 severe that he was thoroughly exhausted. 

 The result showed that the subject dur- 

 ing the periods of rest gained about half 

 an ounce of protein and lost not far from 

 the same quantity of fat daily. The diet 

 which was roughly calculated in advance 

 to be verj^ nearly sufficient for the needs of 

 the organism when no considerable amount 

 of work was done proved to have a slight 

 excess of protein and not quite enough fats 

 and carbohydrates. With the severe men- 

 tal work the results were almost exactly the 

 same. During the 3 days of hard study 

 the organism consumed about the same 

 quantities of nutrients as when it was at 

 rest. Whether this would prove true for a 

 longer period is not certain. 



During the period of hard muscular work 

 the results were quite different. As was to 

 be expected, the food did not sufiBce for the 

 demands of the body. Instead of gaining 

 one-half an ounce, the organism lost about 

 one- sixth of an ounce of protein per day, 

 while the loss of fat reached 6.9 ounces. 

 The fuel value of the materials consumed in 

 the body during the periods of rest and of 

 mental work ranged from 2,600 to 2,700 

 calories per day, but in the period of muscu- 

 lar work it rose to 4,325 calories. In this 

 ease, therefore, the severe muscular work 

 increased the consumption of protein by 

 over half an ounce and the consumption of 

 fats by more than seven ounces per day. The 

 experimenters have estimated the changes 

 which would have been needed in the dailj"- 

 food to make it equal to the demands of the 

 body during the period of muscular work. 

 They calculate, for instance, that if the 

 daily food had been increased by doubling 

 the butter and sugar and adding half a 



pound of bacon it would have been suf- 

 ficient. 



The chief interest of these experiments, 

 from the practical standpoint is the light 

 they throw upon the ways the food is used 

 in the body and the kinds and amounts 

 that are appropriate for people of different 

 occupations and under different circum- 

 stances. Physicians tell us that disease 

 is largely due to errors in diet. It is 

 only by such researches that the exact 

 knowledge can be acquired which is needed 

 to show how our diet can be fitted to the 

 demands of health and strength as well as 

 purse. In addition, the experiments have 

 great scientific interest. 



A number of experiments of this kind 

 have been made in Europe, but these are 

 the first in the United States. These in- 

 vestigations are being continued by the De- 

 partment of Agriculture, and further re- 

 ports may be expected from time to time. 



Thus far we have described only those 

 features of these investigations which in- 

 cluded the measurement of the income and 

 outgo of matter and the determination of 

 the fuel value of the food. The fuel value 

 of excretory products was also determined, 

 as well as the energy manifested by the 

 body in the form of heat or external mus- 

 cular work. For the measurement of the 

 body's energy delicate and elaborate ap- 

 paratus was devised. Highly interesting 

 results have already been obtained, but so 

 many improvements in the methods and 

 apparatus have suggested themselves dur- 

 ing the progress of the work that it has not 

 been deemed advisable to publish the de- 

 tails of this part of the investigation at 

 present. 



AN INDUCTION-COIL METHOD FOB X-BAYS. 

 Since sending a note of a new method of 

 operating an induction coil by the discharge 

 of a condenser we have used it for opera- 

 ting X-ray tubes, and find it gives us a 



