MODIFICATION OF THE GERM-CELLS IN MAMMALS 199 



12. THE BIRTH WEIGHTS AND RATE OF GROWTH IN THE NORMAL 

 AND THE ALCOHOLIC SERIES 



In the present section the birth weights and abihty to grow 

 of the animals born in the normal and the alcohoUc series may be 

 compared. Here again comparisons must be made between ani- 

 mals born in litters of the same size. It may be expressed gen- 

 erally, as was done above for the mortality rate, that the birth 

 weight of an animal, either normal or alcoholic, varies inversely 

 with the size of the litter in which it is born. The average daily 

 increase in weight during the first month varies in the same way. 

 So that when one month old the weight of a guinea-pig also as a 

 rule varies inversely with the size of the litter in which it was 

 born. This condition holds up to three months, at which time 

 the guinea-pig is mature. But the daily gain in weight during 

 the second and third months after birth ceases to be greatest for 

 the members of small litters. Yet the advantage in growth rate 

 €omes to the members of the large litters at so late a time that 

 they are unable to make up their disadvantage sufficiently to equal 

 in size the members of small litters within three months. All of 

 these statements apply equally to both the alcoholic and normal 

 series, and thus the influence of the litter size in general is the 

 same in both cases. 



The question then arises whether there is an actual difference 

 in birth weights and growth rates between the two series. Table 

 8 contains the birth weights of 225 normal control and 531 ani- 

 mals of the alcoholic series. This alcoholic group, as the fore- 

 going tables show, not only includes Fi animals, or offspring from 

 directly treated parents, but also their descendants for several 

 generations, F2, F3, and F4. The animals of both series are 

 arranged in table 8 according to the size litters in which they 

 occur. 



A review of the table shows that the normal series is superior 

 in the average birth weight of the individual and the average 

 birth weight of the entire litter, as well as the average birth 

 weight of the individual born in each of the five different-size 

 litters. 



