1906.] on Some Dietetic Problems. 271 



possible -that some individuals might be "more economical machines" 

 than others, producing, for instance, more work and less heat for a 

 given supply of energy. The human body was certainly not a 

 thermo-dynamic machine ; it might be thermo-electric, chemico- 

 electric, or chemico-dynamic, or even transform energy in some as 

 yet unknown way, and so long as we were ignorant of its exact mode 

 of working, the possibility of variations in the economy of the 

 machine could not be absolutely denied. 



Passing to the income side of the balance sheet, it was shown 

 that this must be determined empirically, by a study of the compo- 

 sition of the diets actually consumed by persons of stationary weight 

 under different conditions. A selection of the results yielded by 

 such study was exhibited with the aid of a diagram, and from them 

 the following " standard diet " had been deduced for a man of 

 average weight, doing a moderate amount of work : — 



Cals. 



Proteid 118 grms. = 484 



Fat 56 „ = 521 



Carbohydrates 500 „ = 2050 



Total energy 3055 



Assuming that the individual whose expenditure was studied in 

 the above balance sheet was put upon such a diet as this he would 

 have a positive balance of 425 calories = 45 grms. fat, or 2 oz. of 

 adipose tissue daily. The question was raised whether this balance 

 was necessarily stored as fat or whether it might not circulate in the 

 blood in some unknown form, and be broken down in abnormal ways 

 giving rise to manifestations of disease. Upon the hypothesis that 

 this could take place Dr. Francis Hare had founded his doctrine of 

 Hyperpyraemia. 



Assuming the standard diet above detailed to be that usually 

 consumed, the further question arose could not economy be effected ? 

 The lecturer suggested two directions in which this was possible : 

 (1) by a lessened heat production, (2) by a reduction of body weight. 

 It was pointed out that in civilised conditions fat had ceased to be of 

 value as a reserve of food, whilst the mere transport of several pounds 

 of it entailed a considerable expenditure of energy. How much fat 

 it was advisable to harbour in the body was an individual question to 

 which no general reply could be given ; it depended upon the " fight- 

 ing weight " of the individual, i.e. the weight at which his mental 

 and physical efficiency was greatest. 



Summing up, the lecturer pointed out that no definite reply could 

 be given to the problem how much energy must be suppUed in the 

 daily ration owing to the great variations in expenditure above de- 

 scribed. Empirical observation showed that 8000 calories was the 

 average amount taken in, but the trend of scientific opinion was in 

 favour of the view that this was perhaps needlessly hberal. 



