126 CHARLES R. STOCKARD AND GEORGE N. PAPANICOLAOU 



In the case of the females an attempt has also been made to 

 lessen the error caused bj^ indiv'dual differences in breeding ca- 

 pacity and in responses to the treatment by using a number of 

 animals. Thirty-four individuals have been treated in all. 

 Many of these females were bred for a number of times as con- 

 trol before being subjected to the fume treatment, after wh ch 

 they are placed of course among the alcoholics. Their earlier 

 breeding records are therefore part of the control data and their 

 subsequent records part of the data included for the alcoho ic 

 lines. The same thing is true of a number of the males men- 

 tioned above. In none of these cases can it be objected that the 

 animals had become too old for normal vigorous breeding while 

 being used in the alcoholic lines. We have constantly guar ed 

 against breeding the alcoholic animals after there is any question 

 as to age affecting their breeding capacities when compared w th 

 the normal breeding cycle of these guinea-pigs. The treat- 

 ment of the large majority of the animals is begun when they are 

 less than one year old, and they have a vigorous breeding span 

 of at least four years. The individua' females wh ch have been 

 subjected to the alcohol fumes are the following: The first six 

 are from the original 1910 stock, Nos. 89, 99, 10 9, 119, 12 9, 

 and 34 9 ; the following twenty-eight are animals reared in the 

 colony or from the newly introduced stocks: Nos. 55 9 , 57 9 , 

 59 9, 60 9, 61 9, 62 9 64 9 , 65 9 66 9 , 88 9 90 9, 117 9, 



NA 

 158 9 , 1619, 654 9 , 847 9 , 865 9 , 946 9 , ^^ 122 9 , 200 9 



^,NA N^ 

 228 9, 397 9, 1139 9, A 796 9 , 1002 9, 1105 9, N v 



^ . A 



1468 9 and 1469 9 . 



There are no contrasts between the histories and capacities 

 of the experimented and control animals that can be fairly ac- 

 counted for as due to differences in either their origins, blood 

 lines, or relationships. As far as experiment and control with 

 biological material may be practically useful, any differences 

 which may exist between the records of the alcoholic guinea- 



