EFFECT OF ALCOHOL ON FOWL 



181 



the mean monthly productions for the full sisters, and only 

 those of the treated birds used to calculate the mean for any 

 month in column 1. In other words, when the ether birds, for 

 example, dropped out by death in April, 1915, all of the untreated 

 control sisters of the ether birds killed were also dropped in 

 calculating the means for the 'Special Control' column. This 

 column gi\'es a critically fair comparison with the treated birds 



NOV DEC JAN FEB MAR APR MAY JUNE JULY AUG SEPT OCT NOV DEC JAN 



Fig. 3 Showing the mean monthly egg production during tlie first 15 months 

 of the experiment. Solid line, untreated controls (data from 'Special Control' 

 column of table 5); dash line, all treated birds; dot line, old general flock data 

 (see text). 



at any stage of the experiments. The columns headed 'N' give 

 in each case the number of surviving birds on which the calcula- 

 tion of the mean was based. 



The data of table 5 are shown graphically in figure 3. In this 

 diagram there has been added the curve of mean monthly pro- 

 duction of the Maine Station Barred Rock stock in earlier years, 

 as given by Pearl and Surface (29, p. 89). This shows clearly 

 enough that the laying of the birds in the experiment as a whole 

 has been excellent. 



