Approximately 0.2 gram of caffein per kilo was employed in these
experiments. Diet and race as possible factors which may influence the
toxicity of caffein were made the subject of study in these experiments
which were divided into two groups as shown in the table, page 25.
_Rabbit 95. Gray and white male. Weight, 1,478 grams. Diet, oats._
February 27: 11.30 a. m., 15 cc 2 per cent caffein (210 mg per kilo)
injected subcutaneously; 2.20 p. m., no symptoms, tremors observed
when handled, but not marked, reflexes slightly increased, no muscular
rigidity nor any other symptoms; 2.45 p. m., rabbit suddenly became
very restless, jumped off the table, and had convulsions; 3.45 p. m.,
rabbit died, rigor mortis set in almost immediately after death.
_Rabbit 96. Gray and white male. Weight, 1,585 grams. Diet, oats._
February 27: 16 cc 2 per cent caffein (200 mg per kilo) injected
subcutaneously at 3.40 p. m.; increased reflexes observed about one
hour after caffein was injected, but no other symptoms.
February 28: Rabbit found dead.
_Rabbit 112. Black female. Weight, 875 grams. Diet, oats._
March 18: 9 cc 2 per cent caffein (205 mg per kilo) injected
subcutaneously at 3 p. m.; 3.30 p. m., rabbit became restless, reflexes
were increased, tremors were observed, but no other symptoms; 4.15 p. m.,
rabbit had tremors, was handled but this failed to induce tetanus,
10 minutes later tetanus of short duration with recovery occurred.
March 19: 9 a. m., found dead.
_Rabbit 119. Yellow white female. Weight, 1,060 grams. Diet, oats._
April 17: 10 cc 2 per cent caffein (188 mg per kilo) injected
subcutaneously at 2.10 p. m.
April 18: Rabbit found dead.
_Rabbit 195. White female. Weight, 1,300 grams. Diet, carrots, since
October 7._
October 14: 13 cc 2 per cent caffein (0.2 gram per kilo) injected
subcutaneously at 11.15 a. m.; 2.25 p. m., rabbit had convulsions and
died. _Note_: Ulceration of rectum was noticed.
_Rabbit 208. Gray. Weight, 1,068 grams. Diet, carrots, October 7-15,
inclusive._
October 15: 10 cc 2 per cent caffein injected subcutaneously at 11
a. m.; 1 p. m., increased reflexes and tremors observed; 3.45 p. m.,
tremors were marked when rabbit was handled.
October 16: Rabbit found dead. _Note_: Looked poorly nourished.
_Rabbit 247. Belgian hare, female. Weight, 1,295 grams. Diet, oats
last 10 days before experiment._
November 10: 11 a. m., urine obtained from the bladder was acid to
litmus and did not contain sugar or albumen, 13 cc 2 per cent caffein
was injected subcutaneously; 1.30 p. m., 15 cc urine obtained was
markedly alkaline to litmus and reduced Fehling's solution; 2.30 p. m.,
reduction of urine considerable, marked tremors observed but no tetanus.
November 11: 10.30 a. m., 95 cc urine collected gave moderate reduction
of Fehling's solution, no symptoms, condition of rabbit seemed to be
good.
_Rabbit 248. Belgian hare, female. Weight, 1,305 grams. Diet, oats the
last 10 days before the experiment._
November 10: 11 a. m., urine markedly acid to litmus, no albumen,
no sugar; 13 cc 2 per cent caffein injected subcutaneously; 1.30 p. m.,
urine was slightly alkaline to litmus, no reduction of Fehling's
solution; 2 p. m., reflexes increased; 2.30 p. m., 2 cc urine obtained
from bladder, sugar abundant; 4.45 p. m., reflexes increased as before,
but no tetanus.
November 11: 10.30 a. m., urine collected showed slight reduction of
Fehling's solution; otherwise condition of rabbit was good; rabbit did
not show any effects of caffein.
_Rabbit 337. Belgian hare. Weight, 1,040 grams. Diet, carrots, March
31 to April 6, inclusive._
April 6: 3 p. m., 11 cc 2 per cent caffein injected subcutaneously in
the back (0.211 per kilo); 4.30 p. m., reflexes much exaggerated.
April 7: 8.15 a. m.; condition good, no symptoms.
_Rabbit 336. Belgian hare. Weight, 1,040 grams. Diet, carrots, March
31 to April 6, inclusive._
April 6: 3 p. m., 11 cc 2 per cent caffein injected subcutaneously into
tissues of the back.
April 7: 8.15 a. m., no symptoms, condition good.
Although symptoms appeared in rabbits of Group I (see table, page 25)
about the same time after the administration of caffein as in the
rabbits of the preceding series all of them terminated fatally 2¼
hours to 24 hours after its administration. Two of these rabbits (Nos.
195 and 208) were fed carrots for several days before the injection of
caffein, the others were fed oats. Since symptoms and death appeared
in these two rabbits about the same time as in the rest of this group
it may be concluded that caffein is not less toxic when carrots are
fed than when oats form the exclusive diet. But since rabbit No. 208
was poorly nourished and ulceration of the rectum was observed in No.
195 it is quite possible that caffein might be less toxic in normal
rabbits on this diet. This was tested in rabbits Nos. 336 and 337, both
of which seemed to be free from abnormality and were well nourished.
Since these rabbits survived and manifested mild symptoms only of
intoxication it would seem that a carrot diet decreases the toxicity of
caffein.
It was suggested, however, that another factor might be the cause of
the greater resistance to caffein in these two rabbits, namely, race.
This was tested in rabbits 247 and 248, both Belgian hares. Since the
toxicity of caffein in these two rabbits was the same as in Nos.
336 and 337, diet as a factor in acute caffein intoxication may be
disregarded. The greater resistance to caffein of these four rabbits
is in all probability due, therefore, to a difference of race. This
suggestion gained additional support from the experiments of the next
series.