METABOLISM, NUTRITION AND DIETETICS 465 



1,300 grammes on the first day of his experiment, and less 

 than 1,000 grammes on the third. 



So much for a purely proteid diet. When fat is given in 

 addition to proteid, nitrogenous equilibrium is attained with 

 a smaller quantity of the latter (7 to 

 15 percent, less). A dog which, with 

 proteid food alone, is putting on flesh, 

 will put on more of it before nitro- 

 genous equilibrium is reached if a 

 considerable quantity of fat be added 

 to its diet. Fat, therefore, economizes 

 proteid to a certain extent, as we 

 have already recognised in the case 

 of the starving animal. On the 

 other hand, when proteid is given 

 in large quantities to a fat animal, 

 the consumption of fat is increased ; 

 and if the food contains little or 

 none, the body-fat will diminish, 

 while at the same time ' flesh ' may 

 be put on. The Banting cure for 

 corpulence consists in putting the FIG. 137. CURVES CON- 



. . STRUCTED TO ILLUSTRATE 



patient upon a diet containing much NITROGENOUS EQUILIB- 



proteid, but little fat or carbo- *' ExPERI ' 



T 



hydrate; and the fact just men- The loss of flesh in grammes 

 tioned throws light upon its action. ^&t^T5 



A 11 ii_ ., i_ u j * r A j diture corresponding to a given 



All that we have here said of fat is true i oss are laid off (in grammes of 

 of carbo-hydrates. To a great extent these 'flesh') along the vertical axis. 

 two kinds of food substances are comple- The continuous curve is the 



, . . curve of income ; the dotted 



mentary. Carbo-hydrates economize pro- curve , O f expenditure. With no 

 teids as fat does, but to a greater extent, income at all the expenditure is 

 and they also economize fat, so that when J^SSS** JU*5 

 a sufficient quantity of starch or sugar is \ s 492 and the loss 12 grammes. 

 given to an otherwise starving animal, all Nitrogenous equilibrium is re- 

 loss of carbon from the body, except that gS?.5^2f^^ 

 which goes off in the urea still excreted, here the two curves cut one 

 can be prevented. Of course the animal another. 

 ultimately dies, because the continuous, though diminished, loss of 

 proteid cannot be made good. 



It is only necessary to add that peptone can, while gelatin cannot, 

 completely replace the natural proteids in the food. Fully five- 

 sixths, however, of the necessary nitrogen may be obtained from 



30 



