In these experiments the resistance of young growing puppies to caffein
was studied. Caffein was given by mouth to all the subjects except one,
to which it was administered subcutaneously. The protocols, only a few
of which are given, and the tabulated data of the experiments (p. 62)
show that the age of the animal has a decided influence on the toxicity
of caffein.
_Dog 11. Weight, 1,260 grams._
August 2: At 10 a. m. given 12.5 cc of 2 per cent of caffein through
stomach tube; 2 p. m., had convulsions, diarrhea, salivation, and
stiffness of limbs.
August 3: Found dead 9 a. m. _Autopsy_: Thoracic viscera apparently
normal; stomach immensely distended and filled with a white, cheesy
mass and some fluid; round worms plentiful in stomach and small
intestine; mucosa of entire intestine congested; contents of lower
intestine congested; liver pale; spleen flabby; kidney congested.
_Dog 10. Weight, 1,650 grams._
July 26: 9.30 a. m., 29 cc of 2 per cent caffein added to 60 cc of milk
offered, but refused, and was therefore fed by mouth through stomach
tube; 10.25 a. m., no symptoms; 11.30 a. m., restlessness, extremities
stiff, post. extremities spread apart, dog shows well-marked symptoms
of caffein poisoning; 12.10 p. m., symptoms more severe, extremities
extended and spread out, is lying flat on belly so that nose touches
floor of the cage; 12.40 p. m., found dead; was alive at 12.10 p. m.
_Autopsy_: Lungs showed hemorrhagic foci in all lobes; heart apparently
normal; liver fatty; stomach and intestines filled with round worms;
spleen and kidney apparently normal.
_Dog 9. Weight, 3,000 grams._
July 25: 350 mg caffein per kilo; 5 p. m., lying down most of the
time, occasionally walks about in stall; restlessness present, but not
marked; 5.30 p. m., vomit which looked frothy and mucilaginous noticed
on the floor of the stall; no meat particles noticed in vomit, though
searched for; whines occasionally.
July 26: 9 a. m., looks well; no signs of the effect of caffein given
the day previous.
_Dog 8. Yellow female. Weight, 3,100 grams._
July 22: 10.50 a. m., received 1.1 grams of caffein in 10 grams of meat
(354 mg caffein per kilo); 3 p. m., vomited mucus; gait clumsy; refused
to eat; continually drinking water; very restless; 4 p. m., convulsions
set in at 3.55 p. m.; tonic rigidity of the posterior extremities;
profuse salivation; convulsions were both tonic and clonic in
character, and resembled those seen in rabbits in caffein intoxication;
a striking feature was the duration of the spasm, which began at 3.55
p. m. and kept up for more than two hours.
July 23: Found dead at 9 a. m.
The data recorded in the table and in the protocols of the experiments
of series C show that four out of the seven animals experimented upon
died in less than 24 hours after caffein was fed; three of these
received 300 to 354 mg caffein per kilo, and one received 200 mg
caffein per kilo. No. 8 vomited four hours after caffein was given.
No vomiting was observed in the other three dogs. From 0.300 to 0.350
gram of caffein per kilo may be regarded, therefore, as surely fatal
to young growing puppies. That this is in all probability the minimum
lethal dose appears from the following experiments: No. 9, which
received 350 mg per kilo, vomited one hour after and survived, which
indicates that some of it was probably not absorbed. The amount which
entered the circulation was therefore less than 350 mg per kilo.
Since No. 15, which received 250 mg caffein subcutaneously, likewise
survived, the probabilities are that 300 to 350 mg per kilo were the
minimum fatal doses for these animals. Moreover, No. 12, which received
200 mg caffein per kilo, survived, no vomiting having been observed.
The case of No. 11, in which the same amount of caffein in proportion
to body weight proved fatal, may be explained perhaps by the findings
of the autopsy.
The results obtained in these experiments justify the conclusion that
young growing dogs can stand larger doses of caffein than full-grown
and older dogs.
Attention may also be called here to the difference in the symptoms
produced by caffein in very young and in adult dogs. It was often
noticed in these experiments that the symptoms in older subjects
when given toxic doses of caffein set in rather abruptly and ended in
instantaneous death. We failed to observe this phenomenon after the
administration of large amounts of caffein to very young dogs, in which
tonic and clonic convulsions alternating with paresis were observed.
These symptoms set in rather gradually and lasted several hours (see
experiment No. 8), resembling the rabbit in this regard.