b THE ELIMINATION OF CAFFEIN. 



with chloroform. It was identified by the use of the murexid test 

 and by precipitation with phosphomolybdic acid. Similar results 

 were reported by Schwenger (13) in individuals drinking coffee, but 

 his conclusions were based on the observation of a precipitate formed 

 by iodin and potassium iodid. 



Schutzkwehr (12), who studied the elimination of caffein in dogs 

 and rabbits, reported its presence in the urine of a dog which received 

 4 grams and of a rabbit which received 0.2 gram of caffein. He 

 stated that he recovered 6 per cent of it in the urine of the rabbit 

 and found a small quantity in the feces. Schneider (11) examined 

 the urine of cats and human urine for caffein at different intervals 

 after its administration. He also studied the elimination of caffein 

 in the cat after administration by different methods, as well as the 

 influence of the size of the dose on elimination. When 30 to 100 

 mg of caffein were given by mouth to these animals some of it was 

 found in the urine at the end of twelve hours, and caffein was still 

 present even after twenty-four hours. When smaller doses were 

 administered none could be detected in the urine. There was 

 apparently a difference in the behavior of caffein in this regard when 

 it was given subcutaneously, as Schneider (11) reported that he 

 could not obtain any caffein from the urine after the subcutaneous 

 injection of 30 mg, but he could detect its presence when 50 mg were 

 thus administered, also stating that he could find it in the urine after 

 two hours. 



In an experiment on a dog to which 100 mg of caffein were admin- 

 istered Maly and Andreasch (10) recovered 66 mg in the urine by 

 chloroform extraction. These investigators maintained that caffein 

 is not decomposed in the body. 



The subject was studied more extensively by Host, who made 

 experiments on the elimination of caffein in rabbits, cats, dogs, and 

 man. According to his report five rabbits, which received 0.2 gram 

 caffein subcutaneously, eliminated in the urine from 11.1 to 21.3 per 

 cent of the amount administered. The quantities recovered in the 

 urine of different animals during the first twenty-four hours varied 

 between 15 and 6.5 per cent, while during the second twenty-four 

 hours from 1.5 to 5 per cent were found in the urine. Small amounts 

 of caffein — 1 to 4 mg — were also found in the urine at the end of 

 seventy- two hours. 



Exceptionally the elimination of caffein may continue beyond 

 seventy- two hours. Thus an examination of the urine collected 

 from two rabbits for Hve days showed the presence of larger amounts 

 of caffein than the urine of two rabbits obtained in seventy-two 

 hours. This, however, is not always the case, as shown by Rost in 

 other experiments. Since the treatment of the animal may prove 

 to be an important factor in the elimination of caffein, it may be 



