154 'Journal of Coinparative Neurology and Psychology. 



become normal to the given age.^ Whether or not this definite 

 relation between the brain and body weights can still be maintained 

 even when we modify the conditions in other ways will be the 

 subject of further investigations. 



Percentage of water in the central nervous system. — The per- 

 centage of water in the central nervous system was always higher 

 in the stunted rats than in the first controls, despite the fact that 

 ages of the two groups were the same. On the other hand, this 

 value in the stunted rats — though shghtly less — was very close to 

 that of the second controls which were much younger. It has 

 been established in the laboratory that among rats of the same 

 age, those with heavier brains have a smaller percentage of water 

 than those with lighter brains. Therefore the higher percentage 

 of water in the stunted rats as compared with the first controls 

 indicates "a usual" rather than "an unusual" condition, since 

 we should expect to find a somewhat higher percentage of water 

 in the rats with less heavy brain at a given age. We conclude 

 therefore that the percentage of water in the central nervous 

 system in both the controls and stunted rats is normal, in the 

 latter of course having due regard for age and body weight, as 

 well as weights of the brain and spinal cord. 



Since the percentage of water and that of the extract are in- 

 versely related we may infer that somewhat greater percentage 

 of water found in the central nervous system in the stunted rat 

 indicates with highest probability relatively smaller development 

 of the medullated nerve fibers in that organ when compared with 

 that of the first controls. This statement is correct at least for 

 the peripheral system, as a recent investigation^ by Mrs. J. W. 

 Hayes shows that the number of medullated fibers in the second 

 spinal nerve in heavier albino rats is greater than that in the less 

 heavy rats of the same age. A further discussion of this general 

 point is however reserved for a future publication. 



Conclusions. — Our final conclusions are, then, that aside from 

 the shorter length in the body and tail, which is not only absolute 

 but relative also, the stunted rats differ from the normal rats only 

 in the absolute magnitude of the measured characters, while, on 

 the other hand, when differences in the central nervous system 



' Effect of partial starvation followed by a return to normal diet on the growth of the body and 

 central nervous system of albino rats. American Journal of Physiology, vol. 17, no. 5. 1907. 

 ■• As yet unpublished. 



