EFFECTS OF INANITION IN THE PREGNANT ALBINO RAT. 101 



normal calves resulted. Osborne and Mendel (1914) have shown that the maize 

 kernel (corn) is deficient in certain salts and amino acids which are necessary to 

 normal growth (in the rat) . 



From my data on the weights of individual rats from mothers starved during 

 the last half of pregnancy, the average gross weight of the newborn is approximately 

 3 grams. The average gross weight of the normal newborn rat in the same colony 

 has been found to be approximately 5 grams (Stewart, 1918a) , the average in my 10 

 normal newborn being 4.92 grams. Consequently, underfeeding during the last 

 half of pregnancy apparently causes a reduction of about 40 per cent in the average 

 birth-weight of the newborn albino rat. The gross body-weight of the individual 

 test rats ranged from 2.1 to 4.4 grams. The average percentage loss of weight of 

 the mother during starvation (table 1) was 28 per cent, the loss ranging from 11 to 

 39 per cent. There is no constant relation between the loss in body-weight ot the 

 mother and the size of the newborn or the number in the litter. However, it 

 should be noted that in general the percentage loss of weight was greatest in the 

 heaviest rats which frequently bore the heaviest fetuses. Also, as might be ex- 

 pected, the weight of the newborn tends to be inversely proportional to the loss in 

 the weight of the mother. Thus, the heaviest newborns (4.3 grams) were from a 

 mother losing only 11 per cent in weight. 



Just what effect this loss or retardation in birth-weight has upon the relative 

 weights of the various parts, systems, and organs of the newborn rat (or other 

 animals) has not hitherto been ascertained, so far as appears from the available 

 literature. These effects of prenatal starvation, and a comparison of the results 

 obtained in postnatal starvation, will now be considered tor the various organs 

 and parts. In each case the data for the normal newborn will be given first; then 

 the prenatal norm, and finally the condition in the corresponding groups of test rats 

 w'll be compared. This will enable us to see whether, in these stunted test rats 

 with retarded body-weight, the various parts retain their normal proportions, as 

 found in the normal (younger) fetuses of the same body-weight; or, it not, the 

 character and extent of the disproportions which have arisen. Finally, a com- 

 parison will be made with the known effects ot postnatal inanition. 



RELATIVE WEIGHTS AND LENGTHS OF BODY PARTS. 



Ratio of body-weight to body-length. — In the 10 normal newborn rats dissected, 

 the average body length was 51 mm. (net body-weight 4.92 grams) ; Stewart (1918a), 

 using litters from the same colony, found the average body-length to be 50.3 mm. 

 (net body-weight 5.03 grams.) 



The ratio of the body-weight (grams) to the body-length (millimeters) in my 

 newborns was 0.096. In Stewart's series (1918a) the ratio is 0.099. The Wistar 

 norm ratio (Donaldson, 1915) is 0.10 tor a 51 mm. rat. In my prenatal fetal controls 

 (table 5), the ratio of the body-weight to the body-length is 0.061 in Group I, and 

 increases through all the groups until in Group V it is 0.092. The ratio for the test 

 rats in Group I is 0.061 and increases through all the groups at nearly the same rate 

 as the prenatal controls to 0.089 in Group V. 



