332 CHESTER A. STEWART 
normally open in the albino rat. Jackson (’12) states that the 
eyes are opened at about sixteen or seventeen days of age. Don- 
aldson (15) (‘The Rat,’ p. 19) states that the eyes open from the 
fourteenth to the seventeenth days, most often on the fifteenth 
or sixteenth. 
King (16) states that usually the female rats in a litter open 
their eyes several hours sooner than do the males. The delay 
in the opening of the eyelids observed in my test rats apparently 
is not because the data, include a large majority of females, for 
TABLE 3 
Age and gross body weight at which the eyelids opened in the control and tests rats 
CONTROLS TEST RATS 
Number of : Number of : 
Litter number individuals oe hee specs individuals Bee sed el) 
grams grams 
St 56 1(F) 15 16.0 3(1 M, 2 F) 18 7.9 
St 59 1(F) 15 3 8(1 M, 7 F) 18 8.6 
St 63 1(F) IGS 15.5-- 2(F) 15 12.2 
St 68 1(M) iF 20.0 1(F) 18 14.0 
St 92 2(1M,1F)| 15 20.0 2(1M, 1F) 16 11.0 
St 95 1(M) 18 11.0 
St 102 1(F) 14 15.0 6(F) 17 10.2 
St 106 1(F) 14 15.0 2(1M,1F) 19 10.5 
St 114 2(1M,1F)| 15 15.8 
Average*.| 10(83M,7F)| 15 16.5 25(5 M, 20 F) 1725 9.9 
* Control of Litter St 63 excluded from the averages, as the exact time at 
which the eyelids opened was not recorded. 
in practically every instance (see exception noted) the eyelids 
opened two or three days later in the test females than in the 
female controls of the same litter. 
THYROID GLAND 
In the test rats fasting from birth to three, six and ten weeks 
of age the weight of the thyroid gland (table 2) is practically 
identical with that in the controls. However, in the rats under- 
fed for very long periods, in which the experiments started at 
three weeks of age, the weight of the thyroid in most instances 
