As already pointed out in the experiments on acute toxicity of caffein, young growing dogs are probably more resistant to caffein than adults. That this may also hold true in chronic caffein intoxication seemed indicated by the following experiments.
Dog 33. Black female puppy. Weight, 4 kilos. Had been continuously on a meat diet.
December 22: 2.30 p. m., received 0.69 gram of caffein (0.172 gram per kilo); 3.15 p. m., no symptoms except that feces were fetid.
December 23: 11.30 a. m., received 0.79 gram of caffein (0.197 gram per kilo); 1.30 p. m., no symptoms.
December 24: 11 a. m., received 0.87 gram of caffein (0.2009 gram per kilo); 4 p. m., no symptoms.
It will be observed that the only effect produced in dog 33 by feeding caffein was increased intestinal putrefaction, although 2.37 grams of caffein were given in three days. Additional data on the effects of the age of animals on the resistance to caffein seemed desirable. The following experiments were therefore carried out. Six puppies of the same litter were weaned when 7 to 8 weeks old and put on a milk diet. Three of them received this diet throughout the experimental period. Meat was substituted in the other three a few days before the administration of caffein was begun, and was continued until the end of the experiment. Caffein was given by mouth; the initial dose, which was administered for several days and then gradually increased, being 160 to 200 mg for each dog, except one, which received only 100 mg per kilo for several days and then an increased amount.
An intermission of a few days (during which no caffein was given) was allowed. This was done on account of some studies carried on at the same time on the effect of caffein on certain constituents of the urine.
| PUP NO. 1. | ||||
|---|---|---|---|---|
| Date. | Weight. | Food (milk). | Treatment (2 per cent caffein). | Symptoms. |
| Grams. | cc. | cc. | ||
| Apr. 21 | 1,450 | 300 | 10.0 | No symptoms. |
| Apr. 22 | 1,520 | 300 | 10.0 | Do, |
| Apr. 23 | 1,450 | 250 | 10.0 | Do, |
| Apr. 24 | 1,375 | 250 | 10.0 | Do, |
| Apr. 25 | 1,420 | 250 | 10.0 | Do, |
| Apr. 26 | 1,390 | 250 | None. | |
| Apr. 27 | 1,400 | 250 | None. | |
| Apr. 28 | 1,405 | 250 | None. | |
| Apr. 29 | 1,420 | 250 | None. | Passed worms. |
| Apr. 30 | 1,430 | 250 | None. | Do, |
| May 1 | 1,450 | 250 | 10.0 | No symptoms. |
| May 2 | 1,515 | 250 | 15.0 | Do, |
| May 3 | 1,475 | 250 | 15.0 | Do, |
| May 4 | 1,495 | 250 | 15.0 | Do, |
| May 5 | 1,515 | 250 | 22.0 | Seems dull and whines. |
| May 6 | 1,535 | 250 | 20.0 | Whines. |
| May 7 | 1,525 | 250 | 20.0 | No symptoms. |
| May 8 | 1,530 | 250 | 20.0 | Do, |
| May 9 | 1,500 | 250 | 23.0 | Diarrhea; passed worms; tremor and rigidity of legs; whines. |
| May 10 | 1,490 | 250 | None. | Completely recovered from the effects of 9th. |
| May 11 | 1,535 | 250 | 25.0 | Can not balance itself; continually vomiting. |
| May 12 | 1,460 | 300 | None. | Recovered from effects. |
| May 13 | 1,475 | 350 | None. | In good condition. |
| May 14 | 1,545 | 250 | None. | |
| May 15 | 1,550 | 250 | None. | |
| May 16 | 1,555 | 250 | None. | |
| May 17 | 1,560 | 250 | 25.0 | Salivated in cage; stiffness of muscles. |
| May 18 | 1,450 | 250 | None. | Weak and stiff; diarrhea. |
| May 19 | 1,500 | 250 | None. | No symptoms. |
| May 20 | 1,565 | 250 | None. | |
| May 21 | 1,545 | 250 | None. | |
| May 22 | (1) | 250 | None. | |
| May 23 | 1,595 | 250 | 27.0 | Tremors; gait clumsy; incoordination of movements. |
| May 24 | 1,495 | 250 | 27.0 | Diarrhea; vomited; weak and stiff; found dead 9 a. m. 25th. |
1 Sunday.