10S EFFECTS OF INANITION IN THE PREGNANT ALBINO RAT. 



Musculature. — The musculature was not weighed separately, but was weighed 

 together with the skeleton and its weight obtained by subtracting the latter from the 

 combined weight. The weight given by Jackson and Lowrey (1912) for the new- 

 born rat is 1.15 grams or 24 per cent of body-weight, 5.3 grams; while in my new- 

 borns the weight of the musculature was 1 .77 grams or 36 per cent of the body-weight, 

 4.92 grams. This marked difference is probably due to a variation in technique, as 

 in all my rats the fat was included with the musculature. The reason for this 

 difference in technique is obvious, because in the small rats the fat was poorly dif- 

 ferentiated from the muscle. 



In my prenatal controls the musculature forms 28, 32, 32, 36.5, and 37.5 per 

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

 Thus in the prenatal controls it is evident that the relative weight of the muscu- 

 lature is less in the smaller rats, increasing progressively up to birth. 



In my test rats the musculature forms 28, 30, 31, 33, and 34 per cent of the 

 body-weight in Groups I toV, respectively (computed from table 5). Thus, in both 

 the test rats and prenatal controls there is apparently an increasing tendency for 

 the musculature to make up a larger proportion of the body-weight as the rat 

 increases in size; that is, the muscle is growing at a relatively faster rate than the 

 remainder of the body, the increase being slightly more marked in the prenatal 

 controls than in the test rats. 



The absolute weight of the musculature in the test rats is slightly below that of 

 the prenatal controls with the exception of Group I (see table 5), in which its absolute 

 weight in the test rats is 7 per cent above that in the prenatal controls. Taking the 

 groups as o whole, the absolute weight of the musculature in the test rats is but 5 

 per cent below that in the prenatal controls. This difference is slight, and may in 

 part be due to a decrease in the fat in the test rats. On account of the difficulties 

 encountered in separating the fat from the musculature, they were weighed together, 

 as previously stated. 



In postnatal inanition in young rats, there is apparently a slight gain in weight 

 of the musculature. It shows an increase of but 6, 8, 10, and 3 per cent, respectively, 

 in rats underfed from birth to 16 days, from birth to 3 weeks, from birth to 10 

 weeks, and from 3 to 10 weeks of age (Stewart, 1918, 1918«; Jackson, 1915a) . The 

 greatest gain observed (25 per cent) was in rats underfed from 10 weeks to 8 months 

 of age (Jackson, 1915a). In both acute and chronic inanition in adult rats the mus- 

 culature loses in about the same proportion as the body as a whole (Jackson, 1915). 



In general, it appears that the musculature manifests a relatively weak growth 

 tendency during both prenatal and postnatal inanition, with even a slight loss in the 



former. 



Visceral group.— The visceral group includes the brain, spinal cord, eyeballs, 

 and thyroid, as well as the abdominal and thoracic viscera. Jackson and Lowrey 

 (1912) give the weight of the visceral group in the newborn as 0.954 gram, or 18 per 

 cent of the body-weight, 5.3 grams. Stewart (1918a) gives the visceral group a 



