EFFECTS OF INANITION IN THE PREGNANT ALBINO RAT. 103 



In my test rats the average weight of the head forms 24.0, 24.1, 23.5, 22.3, 

 and 22.0 per cent of the body-weight from Group I to Group V, respectively (com- 

 puted from table 5) . Therefore, the relative weight of the head is slightly higher in 

 the test rat than in the prenatal controls (except in Group I). 



The absolute weight of the head in the test rats exceeds that of the correspond- 

 ing prenatal controls by 2.8, 6.0, 3.8, 6.5, and 7.6 per cent in groups I, II, III, IV, 

 and V, respectively, averaging 5.3 per cent above in the test rats. Thus in prenatal 

 inanition the head shows a slight increase in weight, which is due partly to the in- 

 crease in weight of the brain, eyeballs, and the integument covering the head. 



In postnatal inanition in young rats, a stronger tendency for the head to in- 

 crease in weight, even when the body-weight has been held constant, has been noted 

 (table 6). Stewart (1918a) found the head to increase 45 per cent in weight (as 

 compared with controls of the same body-weight) in rats held at a constant body- 

 weight from birth to 16 days. In a series of rats stunted by underfeeding from birth 

 to 3 weeks (body- weight 10 grams), the average increase in the weight of the head 

 was 16 per cent, as compared with controls of the same body-weight. In rats 

 underfed from age of 3 to 10 weeks, there was an apparent increase in head-weight 

 of 2.1 per cent as compared with controls of the same body-weight (Jackson, 1915a). 

 This slight gain in weight is attributed to the slight gain in skeletal weight, which in 

 the head probably overbalances the loss in weight of the integument. 



In both acute and chronic inanition in adult rats, the head increases markedly 

 in relative weight and loses slightly in absolute weight (Jackson, 1915). 



From the foregoing it appears that the head manifests its strongest relative 

 growth tendency in rats underfed from birth to 16 days. That this growth ten- 

 dency, though apparently less intense, is present before birth is evidenced by the 

 increase of the head-weight of the test rats as compared with prenatal controls of the 

 same body-weight. 



Extremities and trunk. — In my normal newborn series, the fore limbs form 7.0 

 per cent and the hind limbs 7.6 per cent of the body-weight, 4.92 grams. This is a 

 lower relative weight than given by Jackson and Lowrey (1912) for the relative 

 weight of the extremities in the newborn rat of 5.3 grams, their figures being 7.39 

 and 9.45 per cent for the fore and hind limbs, respectively. This difference is prob- 

 ably due to a variation in technique. Although the fore and hind limbs were 

 always severed from the body at the shoulder and hip joints, respectively, it was 

 extremely difficult to leave the same amount of skin and muscle attached to the 

 limb in each case. 



In my prenatal controls, the fore limbs form 5.3, 6.8, 7.4, 6.7, and 7.1 per cent of 

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

 relative weight of the fore limbs in the smaller prenatal control fetuses is less than in 

 the normal newborn, but this difference (in relative weight) decreases with the in- 

 crease in the size of the fetus. 



In the test rats, the fore limbs form 6.8, 6.8, 7.2, 7.3, and 7.1 per cent of the 

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



