1010] 



ANIMAL PRODITCTION". 



863 



Further studies on the modification of the germ cells in mammals. — The 

 effect of alcohol on treated guinea pigs and their descendants, C. R. Stock- 

 AKD and G. N. Papanicolaou (Jour. Expt. ZooL, 26 {1918), No. 1, pp. 119-226, 

 flfjs. 8). — The authors present the results obtained during the sixth and seventh 

 years of a study of the descendants of a number of gaiinea pigs that had been 

 caused to inhale fumes of ethyl alcohol for an hour or more sis days a week 

 during periods of several months. The results of earlier years have been 

 noted (E. R. S., 35, p. 65). 



The report deals mostly with 594 progeny of alcoholic lines (four genera- 

 tions) and 233 of untreated lines, both stocks systematically mated to avoid 

 inbreeding, but some information is also furnished concerning 302 individuals 

 of inbred alcoholic stock and 41 untreated inbred animals. Since the previous 

 report the mating technique has been improved through a study of the estrus 

 cycle (E. R. S.. 40. p. 4G7). Matings were made by placing a female in 

 heat alone in a cage with a male. If a month later upon careful physical 

 examination she was found to be pregnant, the mating was considered suc- 

 cessful and the number of progeny produced was reckoned as of that date. 

 The number of fetuses in utero was determined by palpation at intervals 

 until parturition and a careful watch was kept for abortions. The young not 

 accounted for at birth were assumed to have died and been absorbed in the 

 manner discussed by Meyer (E. R. S.. 40, p. 663). The accuracy of the palpa- 

 tion counts was checked by a number of autopsies of pregnant females. 



The data from the noninbred stock are tabiilated in three different ways 

 according to (1) the number of generations since the most recent alcoholic 

 ancestor without regard to the latter's sex, (2) whether the paternal or ma- 

 ternal stock or both were alcoholic, without distinguishing between genera- 

 tions except the immediate parents, and (3) whether the alcoholic ancestors 

 were exclusively males, exclusively females, or of both sexes, likewise without 

 discriminating between the more remote generations. The third method shows 

 perhaps the most striking differences and is summarized below : 



Co-ndition of young from matings of guinea pigs exposed to alcohol or descended 



from alcoholic stock. 



1 One month after opportunity for copulation. 



No litters of more than five young were observed in these experiments. Since 

 the death rate was higher in large than in small litters, and since the pro- 

 portion of large litters varied in the different groups of matings, it was neces- 

 sary to eliminate as far as possible the influence of litter size from the mortality 

 data. As used in the table, the relative corrected death rate of the young of 

 a particular group expresses the observed death rate as a percentage of the 



