October 23: Died; was much emaciated but did not show any symptoms; emaciation set in when caffein was withdrawn; urine never contained sugar or albumen; symptoms observed after second dose only.

Series B.

The question whether caffein is cumulative in the rabbit, suggested in the preceding experiments, was the subject of further investigation in Series B. Caffein was given by mouth or subcutaneously. Carrots formed the exclusive diet, a measured amount being given. The rabbits were kept under observation for two weeks, except Nos. 370 and 373, records of which were made only for four days before the administration of caffein was begun. Caffein was given by mouth in experiments of Groups I and III. Rabbits 292, 293, and 295 received daily 20 cc water by mouth for four days previous to the administration of caffein, while in the rabbits of Group II the caffein treatment was preceded by the injection of 0.8 per cent salt solution subcutaneously. The object in both cases was to ascertain whether or not the method of the administration of caffein has any influence on the animal, but observation made from day to day failed to show any effect of such treatment. About 1 decigram of caffein per kilo was administered daily, with occasional intermissions. Later in the course of the experiment the doses were increased, 0.15 gram per kilo being the maximum dose given. Rabbit 293 died after the third dose with symptoms of typical caffein poisoning. The administration of the same dose of caffein was continued 10 days longer in Nos. 292 and 295. It was omitted on the seventh, fourteenth, and fifteenth days of the experiment. On the eighteenth day of the experiment the dose was increased to 150 mg per kilo and was repeated 2 days later. No. 295 was found dead the next day. No. 292 survived. Rabbits 313 and 315 may be considered together, as they were treated alike in every respect. The initial dose of 100 mg caffein per kilo was finally increased to 122 mg. After the twelfth dose the emaciation was well marked and the rabbits were very weak. No. 313 was found dead 2 days, and No. 315 3 days, after the last dose of caffein was given. It should be remarked in this connection that symptoms of caffein poisoning were never observed in these rabbits. Death was not due, therefore, primarily to caffein, but the rapid loss of flesh and strength observed during the last few days suggests that it was due to malnutrition apparently brought about by caffein.

The results obtained by subcutaneous injection of caffein are given in the table as Group II. The initial dose of 100 mg per kilo was injected daily. No. 298 died after the second dose. Nos. 223 and 296 received this amount daily for 6 days. An intermission of 2 days followed, at the end of which the same dose was given again. The next day it was increased to 150 mg per kilo, but no effect was observed; 48 hours later this dose was repeated. No. 223 was found dead, but its mate survived. Symptoms of acute caffein intoxication were not observed in any of these rabbits. It would seem, therefore, that caffein is not cumulative. This supposition, however, appears somewhat contradictory in view of the fact that out of the eight rabbits of this series six died, nor could any cause of death be ascribed other than caffein. Also the first results of Experiments 293, 370, and 373 might be considered as indicating that cumulation, though to a moderate extent, does take place, since in these cases reflexes developed after the drug was given for some time. But this view is contradicted by the results of Experiment 371, in which 150 mg per kilo given 5 days after the daily dosage of caffein was suspended likewise caused increased reflexes. Cumulation, therefore, does not account for the effects noted in the other rabbit. It will be observed that rabbit No. 370, as well as Nos. 371 and 373, had diarrhea for several days. It is quite possible that the weakened condition rendered the rabbits more sensitive to the action of the drug. This is made highly probable by the observations recorded in the experiments on acute intoxication with caffein in which death occurred after small doses. In such cases some pathological condition was often disclosed by the autopsy. The results of this series corroborate, therefore, those of Series A, and indicate again the absence of cumulative action. The results obtained are in all probability due to malnutrition and other conditions brought about by congestion of the viscera and consequent injury to the gastro-intestinal canal.

Table 16.—Chronic caffein intoxication of rabbits; Series B on cumulation.

Group I. Group II. Group III.
Data. No. 292. No. 293. No. 295. No. 296. No. 223. No. 298. No. 315. No. 313.
Diet (grams carrots in 2 days) 1,000 1,000 975 930 905 880 355 300
Caffein administered (cc) and weight (grams):
Mar. 5
1,410 1,470 1,045 1,040 1,070 955 770 770
Mar. 7
1,415 1,360 1,140 1,090 1,095 1,000 715 690
Mar. 9
1,350 1,270 1,070 1,000 1,055 1,005 655 665
Mar. 11
1,505 1,465 1,190 1,230 1,285 1,250 755 760
Mar. 16
1,580 1,460 1,230 1,165 1,170 1,145 730 745
Mar. 17
1,515 1,415 1,080 1,040 1,115 1,105 720 685
Mar. 19
1,565 1,570 1,280 1,195 1,235 1,220 710 735
Mar. 21 7 7 6 4 4
1,585 1,530 1,265 1,150 1,215 1,260 755 700
Mar. 22 7 7 6 (1) (1) (1) 4 4
1,440 1,315 1,175 1,100 1,045 1,150 675 635
Mar. 23 7 7 6 (1) (1) (1) 4 4
1,335 1,140 1,110 1,145 1,190 1,230 715 700
Mar. 24 7 6 (1) (1) (1) 4 4
1,310 (2) 1,090 1,115 1,170 1,250 680 650
Mar. 25 7 6 (1) (1) (1) 4 4
1,375 1,035 1,125 1,215 1,215 695 685
Mar. 26 7 6 4
1,255 1,095 1,105 1,155 1,150 675 695
Mar. 27
Mar. 28 7 6 5.5 6 6 4 4
1,355 1,115 1,120 1,160 1,155 595 685
Mar. 29 7 6 6 6 5 4 4
1,385 1,150 1,155 1,165 955 695 675
Mar. 30 7 6 6 6 4 4
1,330 1,075 1,035 1,095 Dead. 630 610
Mar. 31 7 6 6 6 4 4
1,325 1,170 1,110 1,140 690 605
Apr. (1) 7 6 6 6 4 4
1,335 1,050 1,050 1,120 625 620
Apr. 2 7 6 6 6 4 4
1,390 1,125 1,090 1,155 695 625
Apr. 3
.. 200 ...
Apr. 4
1,300 1,005 1,105 1,080 585 580
Apr. 5 7 6 6 6 4 4
1,385 1,090 1,130 1,090 655 630
Apr. 6 9 7.5 7.5 8
1,260 .. 1,010 1,050 1,110 560 530
Apr. 7
(3)
Apr. 8 9 7.5 7.5 8
1,260 1,000 1.090 1.965 Dead.
Apr. 9 Survived. Dead.Surv. Dead. Dead.

1 On these days 5 cc of salt solution was administered subcutaneously.

2 Dead Mar. 23.

3 Found dead 9 a. m.