Experiments with Tuberculin. 663 



culin was in the system. On the first, second , and fourth occasions 

 in which the system was charg^ed with the tuberculin the milk- 

 yield was above the average, whereas on the third, fifth, sixth 

 and seventh occasions it was below- The highest daily yield 

 (22.25 lbs.) was on the day in the evening of which the first in- 

 jection of tuberculin was made, and the second highest (21.5 lbs.), 

 only three-fourths of a pound less, was on the day after that in- 

 jection. The lowest daily yield (15 lbs.) was on the day when 

 the last injection of tuberculin was in the system, and when be- 

 sides the cow was in heat. This low yield was also reached on 

 the day preceding the second last tuberculin injection (the ninth 

 day after an injection), and also on the succeeding day when the 

 system was charged with this second last injection. This low 

 record could not be justly charged on the tuberculin injection 

 seeing that it was already reached the day before that injection. 



Daisy, like the rest of the herd, was falling off in milk during 

 the experiment, and her average when charged with tuberculin 

 suffers on account of her having reached her lowest mark on Dec. 

 7th on the evening on which a dose of tuberculin was given, and 

 further, that on Dec. 13th the day of the last test, her milk shrank 

 because she was in heat. Taking the seven tests the averages 

 stand thus : 



Average of the seven days following the injections of tuberculin 

 17.82 lbs. 



Average of the forty-seven days for which the milk record is 

 given, 18.26 lbs. This shows a difference of less than half a 

 pound daily on the average against the tuberculin. If we leave 

 out the last injection (Dec. 13th) when the cow was in heat, we 

 find that the average yield per diem for the six days during which 

 the cow was charged with tuberculin is slightly above the average 

 for the whole forty-seven days of the trial. 



Molly, Freda a7id Bertha. These cows were not injected with 

 tuberculin and their milk records have been introduced to show 

 that the daily oscillations in the yield and its progressve diminu- 

 tion in the main during the forty -seven days, was common to the 

 whole herd and in no sense peculiar to the three cows that had 

 been treated with tuberculin. The gradual failure can be seen 

 in the tables. It may be more clearly shown by placing side by 



