128 CM. JACKSON 



ten weeks. In this case the controls are considerably too heavy 

 for direct comparison with the animals under experiment, which 

 accounts for the discrepancy. 



In the anunals held at constant body-weight from the age of 

 three weeks to the ages of six, eight and ten weeks, the visceral 

 group shows a distinct increase in weight. This is more marked 

 at six and eight than at ten weeks, which perhaps indicates that 

 the viscera may increase in the earlier part of the experiment, 

 and lose weight later. The experiment from six to thirty-two 

 weeks indicates no essential change in the weight of the viscera. 

 From ten to thirty-five weeks there is a slight gain. 



On the whole, it may be concluded that during constant body- 

 weight in young albino rats the visceral group as a whole under- 

 goes but little change in weight, with a slight tendency to in- 

 crease, especially in the earlier periods. As will be seen later, 

 however, the individual viscera differ greatly in their reactions. 



Aron ('11) concludes that in young dogs held at nearly constant 

 body-weight the organs in general do not lose weight. On 

 account of the small number of observations, however, and 

 the lack of adequate controls, it is difficult to draw any satis- 

 factory conclusion from his observations upon the viscera. 



The 'remainder' is obtained by deducting from the net body- 

 weight the weight of the integument, skeleton, musculature and 

 viscera. It therefore includes loss by evaporation and escape 

 of fluids, as well as a few small un weighed organs and the masses 

 of dissectable fat. The data in table 9 show a considerable 

 variation, as might be expected. On the whole, however, it 

 appears doubtful whether there is any material change in the 

 weight of the 'remainder' in young rats held at constant body- 

 weight for considerable periods. There is undoubtedly a loss 

 in the fat, but this is probably counterbalanced by an increased 

 water-content of the interstitial connective tissues. 



