318 CHESTER A. STEWART 
RATIO OF TAIL LENGTH TO BODY LENGTH 
Immediately after death each rat was laid on its back and 
gently extended. The distance from the tip of the nose to the 
anus, and from the anus to the tip of the tail was carefully meas- 
ured. From the measurements thus obtained individual ratios 
between tail length and body length were computed. The 
average of these tail ratios expressed as percentage of the nose- 
anus length is given in table 1 for each group of rats. 
The data in table 1 show that with advancing age, the tail ratio 
increases in both the control and test rats. However, as com- 
pared with that in younger controls of corresponding body weight, 
the tail ratio, without exception, is much higher in the test rats. 
At ten weeks of age the ratio for the underfed individuals averages 
approximately 0.78 (73.9 per cent in the males and 82.0 per cent 
in the females), as compared with an average of 0.55 (53.7 per cent 
in the males and 56.6 per cent in the females) for the younger 
controls of corresponding weight. The differences at other ages, 
though somewhat less, are also very pronounced. It is there- 
fore evident that in the underfed rats, the tail continues to grow 
in length more rapidly than the body. Thus the tail ratio in the 
underfed rats at ten weeks (0.78) approaches, but does not quite 
reach, the normal ratio of 0.88 (Jackson ’15 b) for (larger) rats 
of corresponding age. 
In the rats underfed for very long periods, however, the data 
(table 1) indicate an elongation of the tail (ratio 0.89-0.93) even 
beyond the normal ratio for corresponding age. A similar con- 
dition was observed by Jackson (’15 b) in two eases. 
It may further be noted in table 1 that in the controls (except 
at one week of age), and also in the test rats, the tail in most 
instances averages relatively longer in the female than in the 
male. The longer tail in the female, as well as the marked elonga-_ 
tion of the tail in young rats held at maintenance, is in agreement 
with the observations by Jackson (715 b). 
Hatai (08) claimed that feeding rats upon an unsuitable diet 
of starch mixtures produced short-tailed individuals. Hatai 
(15), however, found the tail length in five stunted rats fed upon 
