18 



THE ELIMINATION OF CAFFEIN. 



urine passed was the same during the twenty-four hours after the 

 administration of caffein as in the following period. It is note- 

 worthy that in this series the percentage amount of caffein eliminated 

 was less than in Series VIII. The differences in the amount of urine 

 passed may account, therefore, for the relatively smaller quantity of 

 caffein eliminated in Series IX. 



diet, given 100 mg caffein per kilo 



>o groi 



(Nov. 



25-30}. 



EXPERIMENTS ON GUINEA PIGS (SERIES X AND XI). 



The elimination of caffein in the case of the guinea pig was studied 

 in four series of experiments, in two of which the animals were fed 

 oats while the other two received carrots. The amounts of caffein 

 eliminated varied considerably, 8.43 and 6.36 per cent caffein being 

 found in the first twenty-four hours' urine of guinea pigs fed on car- 

 rots, while those on oats eliminated 4.84 and 5 per cent. In series X 

 the enormous difference in the amount of urine passed by the carrot 

 and oat-fed rabbits and the absence of increased diuresis is of interest 

 in this connection. In the second twenty-four hours much smaller 

 quantities of caffein were found; as shown in the table for series XI, 

 the guinea pigs eating carrots eliminated 1.56 per cent; those on a diet 

 of oats eliminated only 0.55 per cent. There was considerable elimi- 

 nation into the gastrointestinal tract during the first twenty-four 

 hours, almost twice as much on the oats diet as on carrots. This is 

 probably due to better diuresis when carrots were eaten. Examination 

 of the gastrointestinal contents and feces at the end of forty-eight 

 hours showed the presence of small quantities of caffein only 0.5 per 

 cent of the amount injected being recovered in each of the two experi- 



