272 Dr. Robert Hutchison [March 9, 



Turning to the second great problem underlying the science of 

 dietetics — how much proteid is required daily in order to make good 

 the daily waste of the body — the lecturer pointed out that it was 

 impossible to construct a balance sheet for proteid in the body as 

 could be done for energy, for the reason that the organism always 

 tended to get into nitrogenous equilibrium on any quantity of proteid 

 which was supplied up even to the limits of digestive capacity. It 

 was shown by the aid of a diagram that, if an equal number of mole- 

 cules of proteid, carbohydrate and fat w^ere brought into the neigh- 

 bourhood of a cell, the cell did not break down equal proportions of 

 each, but that the highest percentage of proteid molecules was de- 

 stroyed ; next in order of destructibility came carbohydrate, and last 

 fat. This was probably due to the greater instability of the proteid 

 and carbohydrate molecules, an instabihty which, in the case of sugar 

 at all events, was the result of the presence in the molecule of an 

 aldehyde or ketone group. If, on the other hand, a small number of 

 proteid molecules and a relatively large number of those of carbo- 

 hydrate and fat were brought simultaneously within reach of the cell, 

 the mass influence of the more numerous molecules asserted itself 

 and, to use a simile, so distracted the attention of the cell that some 

 of the proteid molecules escaped destruction. Hence the term " pro- 

 teid sparers " as applied to carbohydrates and fats. It was pointed 

 out that the theory of proteid sparers might furnish a reconciliation 

 between apparently opposed systems of diet which yet seemed to give 

 the same therapeutic results. It explained, for instance, how gout, 

 which was presumably due to the presence in the blood of imperfectly 

 oxidised proteid, might be treated successfully either upon a diet con- 

 taining very little total proteid or upon one in which the proteid 

 sparers were largely excluded (e.g. the " Sahsbury " system). Another 

 deduction which might be made from the theory was that it must 

 always be easier to attain nitrogenous equilibrium upon a minimum 

 supply of proteid if the latter was taken along with carbohydrates, so 

 that both nutritive ingredients came under the action of the cells 

 simultaneously. 



Thus to take most of the animal part of the diet at one meal and 

 carbonaceous foods at others was wasteful of proteid, whereas a vege- 

 tarian diet in which carbohydrates and proteid are so intimately mixed 

 that they reach the tissues at the same time, was that on which it was 

 most easy to attain nitrogenous equilibrium on a relatively low proteid 

 intake. 



It followed also from the doctrine of proteid sparers that the 

 amount of proteid necessary for the establishment of nitrogenous 

 equilibrium must vary with the composition of the diet as a whole. 

 It might be supposed that the nitrogenous output of fasting would 

 provide an index of the proteid minimum. This, however, was found 

 by experiment not to hold good, for proteid seemed so to stimulate 

 the vital activity of all the tissues as to increase their power of oxida- 



