July 4, 19 18] 



NATURE 



355 



In view of the shortages of materials and hibour at 

 the present time, no new type can be embarked on 

 unless it is demonstrably superior to existing types 

 and possessed of definite and immediate advantages 

 over them. 



A subject which is intimately connected with the 

 power plant is its noise. This constitutes one of the 

 disadvantages of an aeroplane. For night-flying a 

 method by which it would be possible to hear from 

 one aeroplane the approach of another would be of 

 great advantage. The engine can be silenced without 

 serious disadvantages, but the noise of the propeller 

 and the hum of the wires are so great that silencing 

 the engine is not sufiicient. 



Many jjroposals for the projection of bombs and 

 -tenades of flame and of poisonous gases have been 

 •ceived. The trailing bomb or grapnel for attacking 

 nemy aircraft and submarines is a favourite sugges- 

 ion from inventors. This device was tested before 

 he war and at various times since, but has been 

 ihandoned in favour of more effective methods. 



Many hundreds of inventions and suggestions for 

 iidinometers and instruments for straight flying and 

 accurate bomb-dropping have been investigated. 

 F.fficient and well-designed instruments for these pur- 

 poses have been available for some time past, but it 

 ~ quite possible that improved forms may be pro- 

 duced, though it is scarcely likely that this can be 

 (lone by anyone who does not possess the necessary 

 scientific and mechanical knowledge required for an 

 investigation of this nature. Some inventors entirely 

 disregard the action of centrifugal force upon pendulurn 

 and spirit-level devices. 



A large number of gyroscopic instrurpents liave been 

 proposed which show insufficient knowledge of the 

 rorrect application and limitations of a gvroscope. 



Anti-aircraft devices of various kinds are constantlv 

 suggested, but now contain very little new matter for 

 consideration, as such proposals have received the care- 

 ful attention of the authorities for a long time past, 

 and have been the subject of much trial and experi- 

 ment. 



The Committee fully appreciates the genuinely 

 patriotic motives which inspire most of the communica- 

 tions which they have received, and it is with the 

 object of encouraging the submission of useful and 

 well-considered proposals that this statement is issued. 

 Inventors should, however, bear in mind that the 

 somewhat obvious proposals which might have been 

 useful in an earlier stage of the war are now no 

 longer serviceable. 



FOOD CONSERVATION BY REDUCTION 

 OF RATIONS.^ 



T T is perhaps remarkable that, with all the current 

 ■■■ discussion regarding food conservation, so little 

 emphasis has been laid upon the possibilitv of con- 

 serving food by reducing the diet. When one recalls 

 the agitation of enthusiasts for reduced diets during 

 the past thirty years, and recognises the fact that all 

 special pet theories, can at this psychological moment 

 obtain a better hearing than at any previous time, it 

 is surprising that the advocates of reduced diet have 

 made so little progress, and, indeed, have apparently 

 ceased their propaganda. 



The popular conception that we eat too much is 

 usually quantitatively expressed by the statement that 

 we eat "twice as much as we ought." The nutrition 

 laboratory has for years been endeavouring to discover 



1 Abridged from an address on "Physiological Effects pf a Prolonged 

 Reduction in Diet on Twenty-four Men, " given to the Americ.in Philosophical 

 Society on April 20 by Prof. Francis G. Benedict. (From the Nutrition 

 I,aboratory of the Carnegie Institution of Washington, Boston, Massa- 

 chusetts.) 



NO. 2540, VOL. lOl] 



if there exist any special groups of individuals who 

 live regularly upon a diet that would be commen- 

 surately low. For this purpose it was assumed that 

 , the minimum or basal metabolism must be taken as 

 : the index of food requirement. Differences in 

 j muscular activity are so great that no two individuals 

 ; can be compared save on an absolutely quiescent, 

 ' resting basis. After the metabolism of two hundred 

 or more individuals had been carefully measured, it 

 I was seen that, although we were dealing with people 

 ; of varying ages and dietetic habits, and of supposedly 

 very low metabolism, no such' individuals were easilv 

 ' recognised in our measuiements. It would thus appear 

 offhand that if there are no individuals other than 

 pathological which present abnormally low basal meta- 

 ' holism, and if the law of conservation of energv in 

 the human body obtains, as we know it does, then 

 there is no a priori reason for expecting that a reduced 

 j diet can be permanently adhered to. A reduction in 

 diet will simply mean that body reserves will be drawn 

 upon until death from starvation occurs. 

 ! Through the kind ofiices of Profs. J. H. McCurdy 

 ! and Elmer Berry, of the International Y.M.C.A. Col- 

 I lege at Springfield, Massachusetts, both unusually 

 < interested in metabolism problems, arrangements were 

 made to select twelve men out of a group of volun- 

 : teers from the student body. The men entered heartilv 

 into the spirit of the whole research, and readily con- 

 sented to all the strict requirements of the test. 

 The general plan was to curtail the diet sufficiently 

 ! to reduce the weight approximately 10 per cent. This 

 ! could have been done by a complet^e withdrawal of food 

 . for about fourteen or fifteen days. It was recognised 

 that these men were, first, college students with 

 obligations for educational advancement, and, secondly, 

 volunteers for scientific research. A complete fast for 

 I fourteen days would, in all probability, have caused 

 I most of them considerable discomfort, if not distress. 

 I The alternative was to curtail the dietetic intake so 

 I that the weight-loss would take place, not in fourteen 

 days, but in four to six weeks. This was done by 

 serving the men approximately one-half to two-thirds 

 of the caloric requirements prior to the dietetic con- 

 ; trol, making absolutely no change in the kinds of 

 ! foods eaten. The young men were cautioned not to 

 , lessen their mental or physical activities. Obviously 

 I if the activity of a group of men were lessened, as, 

 i for example, by putting them to bed, to use an extreme 

 j illustration, their dietetic requirements would be very 

 ! much less. Suffice it to say that these men carried 

 out all the requirements of collegiate activity, both 

 physical and intellectual, throughout the entire period. 

 I As soon as the reduction in weight had reached 10 per 

 cent, or thereabouts, the calories in the intak.3 were 

 ! increased to such an extent as to hold the weight at a 

 constant level. The number of calories required to 

 hold this weight constant over a considerable period 

 of time could be taken as a fair representation of the 

 actual caloric requirement for this group of men. 



To ensure a suitable b^se-line, therefore, a second 

 group of twelve men from the large number of volun- 

 teers originally presenting themselves was selected to 

 act as a control squad. These men were in every 

 particular studied with the same degree of care as 

 squad No. i, except that there was no dietetic control. 

 While body-weight can be taken as an approximate 

 index of the metabolic level, further checks were abso- 

 lutely necessary to rule out the inevitable differences 

 in muscular activity that would be found with groups 

 of individuals, even when they were subsisting under 

 the same collegiate conditions. The gaseous meta- 

 bolism was therefore measured practically everv 

 morning for each one of the fiist squad. These 

 measurements were made by collecting the expired air 

 and analysing it. From the amounts of oxygen con- 



