EFFECTS OF INANITION IN THE PREGNANT ALBINO RAT. Ill 



In my prenatal controls the weight of the brain forms 6.2, 5.6, 5.0, 4.8, and 4.4 

 per cent of the body-weight in Groups I to V, respectively (computed from table 5) . 

 Thus in the prenatal controls the relative weight of the brain in the smaller rats 

 (fetuses) is greater than that of the normal newborn, this difference in relative 

 weight decreasing, however, as the birth-weight is approached. 



In my test rats the weight of the brain forms 6.6, 6.2, 5.6, 5.3, and 5.0 per cent 

 of the body-weight in Groups I to V, respectively (computed from table 5). Thus, 

 in the test rats the brain forms a slightly higher per cent ot the body-weight than in 

 the prenatal controls; in both, the smaller the rat, the greater is the weight ot the 

 brain relative to the body-weight. Since in the test rats, especially in the smaller 

 ones, the brain tends to form a relatively larger part of the body-weight than in 

 either the normal newborns or in the prenatal controls, it may be quite safely as- 

 sumed that in a state of inanition of the mother the brain of the fetus has a greater 

 growth tendency than does the remainder of the body as a whole. 



In the test rats the absolute weight of the brain exceeds by 12 to 13 per cent 

 (average 12.5 per cent) that in the corresponding prenatal norms, constantly 

 throughout all the groups (see table 5) . 



Comparing these results with those obtained in postnatal inanition by Jackson 

 and Stewart (see table 6), it is seen that the brain shows its greatest tendency to 

 increase in weight in rats underfed from birth to 16 days (Stewart, 1918a). Here 

 the brain shows a gain of 125 per cent in absolute weight above controls of the same 

 body-weight. This gain drops to 60 per cent in rats (body-weight 10 grams) 

 underfed from birth to 3 weeks (Stewart, 1918) ; and in rats starved from birth to 10 

 weeks the gain is but 8 per cent. In rats underfed from 3 weeks after birth to 10 

 weeks of age the brain shows little or no change (Jackson, 1915a). 



Hatai (1904) found a decrease of 5 per cent in the absolute weight of the brain 

 in young rats losing 30 per cent of their body-weight on an unfavorable diet of 

 starch and beef fat. Later (1908) he found no change in the brain-weight in rats 

 stunted on an unfavorable diet, as compared with normal rats of the same body- 

 weight. 



Donaldson (1911), in young rats held at maintenance from 30 to 51 days ol age, 

 found the brain-weight to average 7 per cent less than in normal controls of the 

 same age. If a comparison is made, however, with the calculated initial brain- 

 weight, as he points out, the average weight of the brain is 3.6 per cent greater in the 

 underfed rats. 



In adult rats, during both acute and chronic inanition, Jackson (1915) observed 

 that the brain even loses slightly in weight. 



From the foregoing results, it may be assumed that in the rat during inanition 

 the brain possesses its strongest growth tendency at birth and that this tendency 

 decreases with age (see table 6) . Whether this growth impulse is stronger or weaker 

 before birth is hard to decide. From a comparison of the data it would seem to be 

 weaker before birth, since in my test rats from underfed mothers the weight ot the 

 absolute brain increased but 12.5 per cent above that of the prenatal norms, while 



