EXPERIMENTS ON RABBITS. 11 



exceeding 2 per cent, and as a rule only about 1 per cent was present,, 

 while in some cases none at all could be detected during this period, 

 so that practically all of the caffein found in the urine is eliminated 

 during the first twenty-four hours after its administration, the rate 

 in all probability being greatest during the first two to three hours. 



The time of the appearance of caffein in the urine has been studied 

 in these experiments and the following data have been obtained. 

 Its presence was detected in some animals fifteen minutes after its 

 administration when carrots were fed. In another series of experi- 

 ments with oats no caffein was found in the urine within fifteen to 

 twenty minutes after injection. After forty minutes, however, as 

 much as 1 per cent was recovered. 



In other experiments performed in this laboratory the presence 

 of caffein in the bile of rabbits and of other animals was detected, 

 the bile of some animals being negative as regards caffein. It 

 seemed desirable, therefore, to determine also whether the gastro- 

 intestinal canal contains caffein after its subcutaneous administration. 

 This experiment was made on two groups of rabbits, one of which was 

 fed carrots and the other oats (Series VII). Caffein was injected 

 subcutaneously, and the rabbits were killed 24 hours later. The 

 amounts found in the contents of the stomach were 1.4 to 1.7 per 

 cent of the quantity injected. In the intestinal contents the quan- 

 tities varied between 1.7 for rabbits on oats and 3.56 per cent for 

 those on carrots. The total amount found in the stomach and intes- 

 tines of some rabbits was about the same as in the urine. 



Series I. 



In the experiments of this series 150 mg of caffein per kilo were 

 given subcutaneously. A total of 760 mg were injected into the 

 three rabbits which received oats. The urine secreted during the 

 first three hours after injection contained 28.8 mg of caffein, or 3.8 

 per cent of the amount injected. The rabbits which were fed carrots 

 received 830 mg of caffein. The urine of the first three hours con- 

 tained 39.3 mg of caffein, or 4.75 per cent. In the next nineteen 

 hours the amounts of caffein eliminated were somewhat more than 

 2 per cent in each case than in the preceding period, thus showing a 

 much faster rate of elimination in the first period as well as a greater 

 amount of caffein being eliminated on carrots than on oats. When 

 the latter were fed the composite urine obtained three hours after 

 injection was 250 cc; when carrots were fed, 360 cc. Better diuresis 

 may explain the difference in the amount of caffein excreted. 



