Two decigrams per kilo were given at first, but it was found that this
amount was surely fatal. The dose was therefore reduced to 0.125 gram
per kilo. In all of these experiments caffein was given by means of a
soft rubber catheter slipped over the stem of a funnel which served as
a stomach tube. A 2 per cent aqueous solution was used throughout these
tests except in one case in which caffein was given mixed with the food.
_Cat 92. Black and white female. Weight, 1,750 grams._
June 10: 12.05 p. m., 14 cc 2 per cent caffein (0.16 gram per kilo)
given by mouth; cat was quiet when tied on holder, struggled only a
little when tube was put into stomach; 12.30 p. m., cat vomited, no
other symptoms.
June 13: Condition good, appetite good.
_Cat 87. White female. Weight, 2,620 grams. Diet, meat._
June 5: 2.15 p. m., 20 cc 2 per cent caffein (0.15 gram per kilo)
solution administered by mouth through stomach tube; 2.30 p. m., cat
irritable, but no other symptoms; 5 p. m., condition about the same,
except that it was more irritable and showed some stiffness of the
extremities.
June 13: Alive and in good condition, appetite good, not irritable.
_Cat 91. White female. Weight, 3,050 grams._
June 10: 12 noon, 23 cc (0.15 gram per kilo) of 2 per cent caffein
administered by mouth, cat struggled violently; 1.30, salivation; 1.40
p. m., convulsions; died at 2 p. m. _Autopsy_: Congestion of lungs,
liver, and spleen; heart vessels injected; other organs normal.
_Cat 88. Black and white female. Weight, 3,260 grams. Diet, meat._
June 5: 2.20 p. m., 25 cc of 2 per cent caffein (0.15 gram per kilo)
given by mouth; 2.45 p. m., cat irritable, no other symptoms (cat did
not vomit after the administration of caffein); 4 p. m., cat found
dead. _Autopsy_: Liver very much congested; heart contracted; body was
still warm at the time of autopsy.
_Cat 90. White and yellow female. Weight, 2,685 grams. Diet, meat._
June 5: 3.15 p. m., 27 cc of 2 per cent caffein (0.2 gram per kilo)
given by mouth through stomach tube, about half an hour later cat
became irritable and began to salivate; at 4.30 p. m. salivation
became more marked, dyspnoea was well developed, and the cat was
quite restless and had tremors; 5 p. m., short spasms of posterior
extremities, but lay quietly in the cage most of the time; 5.20 p. m.,
convulsions of short duration and death, muscular relaxation followed
immediately after convulsions, no vomiting, diarrhea observed after
administration of caffein, and cat passed about 10 cc of urine.
June 6: 9 a. m., found dead.
_Cat 89. White and black female. Weight, 2,860 grams. Diet, meat._
June 5: 3.15 p. m., 28.6 cc (0.2 gram per kilo) of 2 per cent caffein
given by mouth through stomach tube, no vomiting observed, nor any
other symptoms; 3.30, found dead. _Autopsy_: Organs normal; liver
congested.
_Cat 82. Gray female. March 3, weight 2,450 grams; June 6, weight
2,750 grams. Diet, 150 grams of meat daily._
June 7: Given 0.4125 gram of caffein in 150 grams of meat, did not eat.
June 8: Given 0.4125 gram of caffein in 150 grams of meat, refused to
eat.
June 9: Given 150 grams of meat without caffein, ate all of it.
June 10: No food given.
June 11: No food given.
June 12: Given 0.4125 gram caffein in 150 grams of meat (150 mg per
kilo), ate all of it.
June 13: Found dead. _Autopsy_: Lungs congested, liver congested; other
organs apparently normal.
_Cat 100. Gray female. Weight, 2,740 grams. Diet, meat._
July 17: 3 p. m., 17 cc of 2 per cent caffein (124 mg per kilo) given
by mouth through stomach tube at 3.20 p. m.; 5 p. m., very irritable,
but no other symptoms.
July 18: Under observation all day, no symptoms.
_Cat 93. Black and white female. Weight, 1,640 grams._
July 17: 3.30 p. m., 10 cc (0.125 gram per kilo) of 2 per cent caffein
given by mouth through stomach tube.
July 18: Under observation all day, no symptoms.
From the results of the experiments of this series it appears that
0.15 gram caffein per kilo may be fatal within a few hours after its
administration, even if the drug is mixed with a moderate amount of
meat. Experiments 87 and 92 show, however, that this amount may be
borne by some individuals without any serious consequences, as the cats
were under observation for some time after they received caffein, and
no untoward symptoms were noticed in either of them during this time.
It may be remarked that cat No. 92 vomited shortly after it received
caffein. It is practically certain, therefore, that this amount of
caffein in proportion to the weight of the animal will in the great
majority of cases prove fatal, and perhaps in a smaller percentage
of individuals it is surely toxic if it does not escape absorption.
Smaller doses may cause irritability in some individuals, but symptoms
referable to nervous symptoms of muscles were absent, as in experiments
Nos. 93 and 100. The minimum fatal dose of caffein for the cat when
given by mouth is, therefore, 0.15 gram per kilo.