320 CHESTER A. STEWART 
head to become relatively large, due to the very sight loss of the 
head in weight, as compared with the loss in weight of the body 
as a whole. 
EXTREMITIES AND TRUNK 
According to Jackson and Lowrey (712) the upper extremities 
(fore limbs) at one week of age normally form an average of 
8.92 per cent of the body, the average net body weight being 
11.6 grams. In my controls of the same age, but somewhat 
lighter in weight (9.8 grams net), the average relative weight of 
the upper extremities (6.9 per cent) is lower. This difference 
may be due in part to variation in the technique used in removal 
of the extremities, ee in both cases they were divided at the 
shoulder joint. 
As compared with my controls the weight of the upper ex- 
tremities (table 1) is heavier in the test rats underfed from birth 
to three weeks of age. The apparent growth from 0.678 to 0.800 
gram (sexes combined) represents an increase of about 18 per 
cent. In the case of the rats underfed longer periods the weights 
of upper extremities are variable, but in the majority of instances 
they are lighter in the test animals than in the controls. On the 
whole, the differences are not very striking. 
In the case of the lower extremities (table 1), the average 
relative weight of the hind limbs (9.53 per cent) for my controls 
at one week, is slightly lower than the relative weight (11.97 
per cent) obtained by Jackson and Lowrey (’12) for normal rats 
of the same age. | 
As compared with my controls, the data in general indicate no 
distinct change in the weight of the hind limbs in the test rats. 
In the case of the four males underfed until 291 days of age there 
is an apparent increase from 11.58 grams in the controls to 14.20 
grams in the test rats. The lower extremities are also much 
heavier in the females underfed to 314 days of age as compared 
with the younger control of corresponding body weight. At 
all other agés, however, the differences are variable and much 
less marked. 
