JANUARY 26, 1922] 



NATURE 



123 



lowering a weight; and static, such as maintaining a 

 weight. The first two correspond to isotonic condi- 

 tions of contraction, and the last to isometric con- 

 traction. As a measurement of the expenditure of 

 energy in these forms of work a subject was given the 

 task of lifting a weight on his hand, lowering the 

 same weight and holding it steady both in the prone 

 and supine positions, the rate of movement being con- 

 trolled by a metronome : — 



Calories per 

 Form of work sq. m. per hour 



Positive 1509 



Negative 124-5 



Positive and negative 180-5 



Movements without weight 6o-i 



Static 946 



In spite of the apparent severity of static work in 

 producing fatigue the metabolism is not excessive, 

 and the fatigue may be due to interference with the 

 circulation. 



Prof. A. V. Hill showed curves founded on the heat 

 production of isolated frog's muscles, indicating that 

 maintenance of a contraction is expensive, requiring 

 ten times as much energy expenditure. He also gave 

 results obtained by moving a flywheel at different 

 rates of speed. The rapid rates of movement waste 

 energy because the change of form of muscle requires 

 work to be done m overcoming the viscosity of 

 muscle, whilst slower rate of movement allows a 

 larger proportion of energy to appear as external 

 work. It is important to find out the most efficient 

 relation between the work to be done and the rate 

 at which it should be carried out. 



Prof. H. Briggs described the physical endurance 

 tests used during the war. He showed curves relating 

 the variation of energy expended with the work done. 

 A normal load is one which can be continued in- 

 (letinitely. It was found that well-trained men get 

 assistance from breathing oxygen only when doing 

 excessive work, whilst a man in poor condition is 

 helped by breathing oxygen with smaller loads. 

 Stamina is the ability to maintain work. It appears 

 that habitual hard work may maintain a man's 

 stamina to greater ages than 'is found in sedentary 

 individuals. 



Dr. J. S. Haldane quoted experiments on the cir- 

 culatory side of work. These experiments were made 

 on man, the lungs being used as an aerotonometer. 

 With increasing severity of work the blood-flow in- 

 creases exponentially, whilst the percentage of oxygen 

 desaturation of the blood rises logarithmically, and 

 the output per heart-beat remains almost uniform. 

 Therefore, the pulse-rate varies with the blood-flow. 

 In a few individuals in whom the percentage of 

 oxygen utilisation is already high the output of the 

 heart increases as well as the rate of beat. Acapnia 

 decreases circulation-rate, and is thus unfavourable to 

 work. 



Prof. A. V. Hill reported some results on pulse 

 conduction in relation to blood-pressure, using the 

 hot-wire sphygmograph. The pulse conduction can be 

 expressed by 



Vper cent, increase of arterial vjlume per mm. Hg increase in pressure. 



measuring systolic and diastolic pressures and the 

 ' ite of pulse conduction it is possible to estimate 

 I lie increase in volume of the arterial reservoir at 

 each heart-beat. 



Prof. A. D. Waller described the simplified method 



for the estimation of physiological cost of work done 



under various industrial conditions. He suggested 



that, instead of the various arbitrary terms such as 



NO. 2726, VOL. 109] 



sedentary, light, medium, and heavy work, one 

 should use the energy expenditures of 100, 200, 300, 

 and 400 kilogram metres respectively. 



Prof. A. Krogh laid emphasis on the effect of diet 

 on the respiratory quotient and on efficiency. For 

 short experiments a diet containing plenty of carbo- 

 hydrate is better for maintained exertion. He 

 criticised Prof. Waller's technique, but said that it 

 was probably satisfactory for the investigation of 

 energy expenditure under working conditions in in- 

 dustry. Prof. Waller's methods were criticised by 

 several others. Some criticisms were on technical 

 points, such as the accuracy of dry meters, tempera- 

 ture and pressure measurements or the size of bag 

 used in collecting the expired air, and some were on 

 the results, namely, the low carbon dioxide output in 

 his published work. As Prof. Briggs pointed out, 

 there may be greater sources of error neglected by 

 both sets of workers than those due to the errors of 

 analysis. 

 The discussion terminated by a paper on "The 

 I Economy of Human Effort in Industry " by Mr. E. 

 I Farmer. The aim of his study was to find more rapid 

 j methods of carrying out industrial processes. One must 

 j see the effect on output without the stimulus of special 

 ! pay. The principles to be used in devising new 

 I methods are to encourage smooth movements with- 

 ! out marked change in direction and to avoid the inter- 

 vention of discrimination. He gave examples of in- 

 creased output in packing chocolates and in metal 

 f>olishing. Further points requiring study are : What 

 is monotony, what is the influence of noise, and 

 what is the influence of vibration on the workers? 

 A few individual papers were given. 

 Prof. A. Krogh described a simple apparatus, con- 

 sisting of a volume recorder containing soda lime, for 

 measuring oxygen consumption. The soda lime ab- 

 sorbs all carbon dioxide and the volume decrease as 

 recorded on a kymograph gives a measure of the 

 oxygen absorption. 



Dr. J. C. Drummond gave an interesting account 

 of some recent work in connection with vitamins 

 and their relation to public health. Green plants and 

 fruits are the main source of vitamins. Dairy pro- 

 ducts are good in furnishing the vitamins provided 

 that the cows have been fed on green food containing 

 them. The plankton in the sea by the presence of 

 green plants is a source of vitamins which we 

 obtain in fish and fish-oils. It is important that in- 

 dustrial populations should obtain a proper supply of 

 vitamins, because a relative deficiency in them may 

 cause ill-health without the appearance of such 

 diseases as scurvy or beri-beri. 



Dr. F. W. Edridge-Green reported experiments on 

 mixing white light with spectral colours. He was 

 followed by Dr. Shaxby, who described a useful instru- 

 ment consisting of a grating spectroscope with two 

 collimators by which the spectra are formed in re- 

 versed order. By a shutter in the eye-piece it is 

 possible to compare monochromatic patches in re- 

 versed order. 



Dr. R. J. S. McDowall read a paper on "The In- 

 dependence of the Pu'monary Circulation as shown 

 bv the Action of Pituitary Extract." Tracings were 

 shown in which the pulmonary pressure was seen to 

 vary independents of the systemic circulation. 



Dr. E. P. Pouiton and Dr. W. W. Payne read a 

 paper on "Epigastric Pain." They consider that 

 epigastric pain is not necessarily referred pain, but 

 that it may be due to spasmodic contractions of the 

 oesophagus, stomach, or duodenum. 



A number of demonstrations were given, and one 



