152 CHARLES R. STOCKARD AND GEORGE N. PAPANICOLAOU 



in this, but in several of the tables to follow. The prenatal 

 records include embryos that die and are absorbed in utero, 

 never passing to the outside, other embryos and fetuses which 

 die and are passed out or born prematurely, and finally full- 

 term young which die shortly before birth and are, therefore, 

 still born or born dead. The postnatal deaths include all ani- 

 mals dying before reaching three months of age, at which time 

 guinea-pigs are about mature. 



In the control lines 51.92 per cent of the total mortality oc- 

 curred before birth or was prenatal, while 48.08 per cent of the 

 deaths occurred after birth. Considering the numbers in- 

 volved, it therefore may be said that the pre- and postnatal 

 mortalities are about equal in the straight control lines. There 

 is no evidence here of a particular tendency on the part of the 

 young animals to succumb at any given or critical stage in their 

 development. 



The numbers contained in the normal inbred column are cer- 

 tainly too small to be considered. 



In both the alcoholic and the alcoholic inbred lines where the 

 numbers involved are considerable (the records showing 329 

 deaths among 896 animals), the prenatal mortalities are double 

 the postnatal deaths. The alcoholic column shows 70.14 per 

 cent of the total mortality to occur before birth, while only 29.85 

 per cent of the individuals that died were lost after birth. The 

 last column gives for the alcoholic inbred animals 65.25 per cent 

 of the total mortality as prenatal and only 34.74 per cent as 

 postnatal. This consistent arrangement in the two columns 

 indicates a tendency on the part of the weak and subnormal 

 individuals of the alcoholic lines to succumb during early stages 

 of their development. Such an interpretation is exactly in ac- 

 cord with and is substantiated by the high early prenatal mor- 

 tality which exists in these lines as indicated by the size of 

 their litters and frequent mating failures when compared with 

 the control. 



A mortality arrangement of this kind accords with what is 

 known of almost all weak or diseased stocks — there is a very high 

 loss during the early stages of development, as well as during 



