WEIGHTS OF ORGANS IN UNDERFED YOUNG RATS 125 



found that in spite of constant live weight, the animals con- 

 tinued to increase in length and height for three to five months. 

 Thereupon the emaciated animals became weaker and died un- 

 less the amount of food was somewhat increased. From a 

 comparative study of nine bones (the entire skeleton was not 

 measured), Aron concludes that the skeleton during constant 

 body-weight increases in mass and also changes in chemical 

 composition (increase in water-content and protein (?) ; decrease 

 in fat). The results of this very interesting investigation, while 

 sufficient to establish the continued growth of the skeleton, 

 would be more conclusive if the number of observations were 

 larger, with an adequate number of controls at the beginning 

 and at the end of the experiment. In a recent paper, Aron ('14) 

 records a few observations indicating that malnutrition in 

 children retards growth in length less than body-weight; so that 

 the body may continue to increase in length while the body- 

 weight is at a standstill, or even slightly decreasing. Thus the 

 strong growth tendency of the skeleton during bare maintenance 

 of the body-weight is manifest in the human species, as well as 

 in the calves, dogs and rats. 



MUSCULATURE 



Although the musculature (table 8; fig. 4) in the normal rat 

 at three weeks averages 26.9 per cent of the body, according 

 to Jackson and Lowrey ('12), the controls in the present series 

 gave a somewhat higher amount, the average being 31.2 per 

 cent. As shown in table 8, the" musculature in the controls of the 

 present series also averaged slightly higher than the normal 

 according to Jackson and Lowrey at six and ten weeks. In 

 rats held at constant body-weight from the age of three weeks 

 to six, ten and thirteen weeks, the musculature appears relatively 

 very slightly higher than in the controls at three weeks. The 

 apparent increase from three to ten weeks is from 7.40 grams 

 (7.81 grams, less correction corresponding to the smaller body- 

 weight at 10 weeks) to 7.62 grams, or an increase of 3.0 per cent 

 in absolute weight. In the three to sixteen weeks experiment, 



