10 CAFFEIN IN NEPHEECTOMIZED RABBITS. 



of alkaloids, but only within recent years for inorganic substances. 

 In this connection it is of interest to recall the work of Mendel 19 20 21 

 and his collaborators, who have found by experiments on animals 

 that the channel of elimination varies for different inorganic salts, 

 magnesium and calcium salts being eliminated entirely by the kid- 

 ney. According to Hanford, 9 caesium is eliminated by the kidney 

 and bowel. Although Mendel and Thacher 22 found strontium in the 

 urine, it is chiefly eliminated by the bowel, as it was found in greater 

 quantities in the feces after parenteral introduction of its salts. After 

 subcutaneous injection barium is likewise eliminated by the -bowel, 

 and only traces of it appear in the urine. Rubidium, on the other 

 hand, seems to be excreted chiefly in the urine and to a much smaller 

 extent by the bowel. 



Although it is known that alkaloids may be eliminated by the walls 

 of the stomach and intestine in health, very few of them have been 

 investigated in regard to their excretion into the intestines or stomach 

 in abnormal conditions. As pointed out in a previous investigation 27 

 by this laboratory, studies on the elimination of caffein were made 

 by a number of investigators, but for the reasons set forth its rein- 

 vestigation was undertaken. It was found that this substance is 

 eliminated by the stomach and intestine as well as by the kidney, 

 but the relative amounts found in the contents of the gastrointestinal 

 canal, especially in the contents of the intestine, are greater with a 

 diet of oats than with one of carrots. Since this difference in the 

 rate of elimination may be accounted for by the increased activity 

 of the kidney on a diet of carrots, the desirability of testing the 

 eliminative capacity of the gastrointestinal canal of the rabbit for 

 caffein presented itself as affording an opportunity to test the exist- 

 ence of a compensatory mechanism for the elimination of caffein after 

 the removal of both kidneys. 



EXPERIMENTS. 



The experiments were carried out on well-nourished rabbits of 

 medium size, some only 4 or 5 months old, but all apparently in good 

 condition at the time of the experiment. All the operations were 

 performed under ether anaesthesia. Except in one series in which 

 the abdominal route was chosen, the kidneys were removed by 

 lumbar incision. The renal pedicle was securely ligated, the kidney 

 excised and removed, and the wound then closed. With few excep- 

 tions the loss of blood was slight. The animals stood the operations 

 very well; they could walk shortly afterwards, and their general con- 

 dition was very good. The duration of life varied considerably, 

 some living less than 24 hours, but most of them surviving the 

 operation from 2 to 3 days. In some exceptional cases the duration 

 of life was much longer, for one rabbit lived 5 days and another 7 



