NUTRITION AND GROWTH: I. 25 



weight, but if the food was iacreased slightly, it was possible to keep 

 the emaciated animal at a constant weight. 



From the two hundredth until the three hundred and fiftieth da}- — 

 that is, for five months — dog A was kept at a constant weight and there 

 was no noticeable change in its size nor in its appearance; in fact this 

 .constancy indicated a cessation of growth. Therefore we must conclude 

 that it is possible by a suitable restriction of diet to maintain young, 

 growing dogs at a constant weight for considerable lengths of time. A^'liile 

 the weight remains constant, important changes occur in the animal's 

 body. These consist in a continuous increase in the length and height of 

 the dog, combined with a more or less extreme emaciation. 



Apparentl}', in spite of the constancy of weight, the skeleton grows 

 and increases both in size and mass. If this be true, other parts of the 

 body must have lost in mass. In all probability not only the relative 

 masses of the different parts of the body, but also the quantities of the 

 various body constituents, have changed considerably. Information con- 

 cerning these alterations is furnished by the analyses of the bodies of 

 the animals. 



RELATIVE AMOUNT OF CHANGE IN CERTAIN PARTS OF THE BODY AS COMPAEED 



WITH OTHER PARTS. 



The skeletal system shows the most striking difference in general 

 composition. The quantities of jJi'otein and ash in the bones of the 

 three dogs, IV, II, and III, are nearly the same in spite of the differences 

 in weight, number IV, 2,850 grams; number II, 1,940 grams; and nimiber 

 III, 1,750 grams. The weight of the bones (ash and protein) in relation 

 to the live weight is considerably higher in dogs number II and III 

 (9.6 per cent and 9.1 per cent) than in dog number IV ^" (5.8 per cent). 



We find even more pronounced differences in comparing the composi- 

 tions of dogs V and VI. Several corresponding bones of these two 

 animals were isolated and analyzed. The weight of each bone of dog 

 number VI was not much less than was the corresponding bone of dog 

 numberV, although the body weight of the former was 5,885 grams and 

 of the latter 2,710 grams. The total weight of the nine bones selected 

 from the normal dog, number V, was 127.0 grams or 2.16 per cent of the 

 live weight; the bones from the dog of constant weight, number VI, 

 M^eighed 119.4 grams or 4.41 per cent of the live weight. 



In experiment IV, I isolated the corresponding bones from two other 



" The bones of dog number IV contain proportionally more protein and less 

 ash than those of numbers II and III, This fact is still more pronounced in 

 dog number I. These animals were fed on a diet poor in calcium (meat and 

 starch without addition of lime) and the changes in the skeletal system cor- 

 respond to those described by me as occurring as a consequence of such n diet. 



