Abstract
This experiment was made to see whether weight ratios of organs-body and relative sizes of bones to skull length are influenced by the planes of nutrition or not.
Experimental animals were male mice of two inbred strains dd, rr and their reciprocal hybrids F1 dr, rd. They were, within 5 days after their birth, divided into two groups, and were fed respectively with high and low planes up to 60 days of age. The results are as follows:
1. Weight ratios of organs-body were larger in low plane of nutrition than in high one. This seems to be due to the reason that insufficiency of fat and protein in low plane restrains the increase of these in the body, especially in the unmeasured organs, and it naturally restrains the growth of body weight which was used as a denominator.
As for these ratios, strain difference was found between dd and rr. However, no difference was noted between the inbred and its hybrid or between dr and rd.
2. As for relative sizes of partial bones in skull length, few differences were found between high plane of nutrition and low one. This seems to be due to the following reasons; first, these partial bones belong to the same skull as skull length, second, skull completes its growth fairly at an early stage of development, and its growth was scarcely affected by such nutritional conditions as this experiment.
3. On the contrary, length of head and trunk, tail length, femoral length and tibial length continue to grow comparatively later. So these are more affected by nutritional conditions than skull length is. Results that relative sizes of these bones to skull length were larger in high plane than in low one will be explained by the above reason.
