124 CHARLES E. STOCKARD AND GEORGE N. PAPANICOLAOU 



further strengthened by the fact that the same normal males 

 are mated with alcoholic females and with normal females, and 

 normal females are mated with alcoholic males and again with 

 normal males as a control, etc. In this way the experimental and 

 control animals are actually in some cases the same individuals 

 and in all cases they are constantly being bred together. There 

 is no question that the animals treated with alcohol and the 

 control are equally general or random samples of the popula- 

 tion. Yet there is a marked contrast between the records of 

 their offspring and descendants. 



b. Inbreeding 



The alcoholic lines which we shall analyze in detail in the 

 following considerations are practically devoid of inbreeding. 

 Almost all of these animals are known in our colony for three or 

 more parental generations, and we mean in stating that they are 

 not inbred that a gi\'en individual in their ancestry never ap- 

 pears more than once back through the great-grandparent gen- 

 eration. In the first table to be considered the straight alcoholic 

 lines may be compared with other lines that are not only alco- 

 holic, but also inbred, usually to a slight degree, and it is seen 

 that inbreeding in either the alcoholic or the control to a lim- 

 ited degree gives no indication of any significantly injurious 

 effects. 



In our former report ('16) there were shown to be more in- 

 jurious effects in the alcoholic inbred lines than in the non- 

 inbred. This difference has now disappeared on account of the 

 fact that the animals in the former table were more closely in- 

 bred and were earlier generations than the bulk of those in the 

 present consideration. The degree of inbreeding in the inbred 

 lines is now much reduced as compared with the earlier table, 

 and the records have improved. This difference between the 

 earlier and the present results indicates that inbreeding in these 

 alcoholic lines may be easily carried to a degree which will make 

 the injurious effects more marked. We have avoided even the 

 slightest approach to such a degree of inbreeding in the straight 



